Well in the canon timeline it appears that Featherson won North Carolina, Alabama, and Mississippi pretty early on election night. That suggests he was really strong in all three of those states, so I suspect he would at least still win North Carolina and Mississippi in this alternate time line. That gives him an initial 35 electoral votes for the Freedom Party. (Alabama is a little more complicated, so it will be discussed further below.)
I likewise agree with you that the Freedom Party is almost certain to win Texas. It went for Featherston in 1921 and even in 1927, and it elected a Freedom Party Governor in 1925 (and presumably in 1929), so its hard to see Featherston not winning it in the presidential race. That gets the Freedom Party up to 68 EVs.
I would also give the Freedom Party Florida since they seem to be pretty strong there (they carried the state in the 1921 presidential race and elected a Governor there in 1931). Furthermore, with the Freedom Party controlling the Governorship there, they control the State Militia, which means there is no force in the state that will be able to keep the Stalwarts under control. That gets the Freedomites up to 79 EVs.
I rather doubt the Featherston would carry Virginia. Despite it being his home state, Featherston never seemed to do that well there. He didn't carry the state in 1921 or 1927 and in 1931 the Freedom Party failed to elect a Governor there. Plus it's Sam Longstreet's home state, so he should be pretty strong there. So that's 15 EVs for the Whigs.
Likewise as to Arkansas since the Whigs won in the canon timeline, they are certain to win it here as well. That gets them up to an initial 27 EVs.
I agree with Cuba and Louisiana as Radical Liberal states. Chihuahua is more questionable since the Freedom Party won the Governorship there in 1931 which means here also the state militia will be backing the Stalwarts. However, with the Freedom Party less popular in this timeline, it should have both considerably less resources than in the canon timeline (wealthy Confederates are going to be less willing to make donations to a party that murders its political opponents) while also having greater demand on its resources since it is facing a much tougher election in the more populous eastern states. Thus the Freedom Party will have to make some cuts somewhere, and its operations in the Spanish speaking states are the most likely to take that cut. And with favorite son Arango leading the charge against them in the state, it is plausible enough the Rad Libs could pull off the win here.
(I would also likely give the Rad Libs Sonora for the same reason, which bumps the Rad Libs up to an initial total of 47 EVs.
Thus with the Freedom Party at 79 EVs, the Whigs at 27 and the Rad Libs at 47, the election is going to be decided by South Carolina, Georgia, Alabama, and Tennessee.
South Carolina I think goes Freedom. Like Florida, the Freedom Party elected a Governor there in 1931, so again they control the State Militia there and the Stalwarts are free to run wild. That gives the Freedom Party an enormous advantage in the state and should be enough for them to carry the state. That gets Featherston up to 91 EVs.
I doubt the Freedom Party wins Georgia. We never hear about them having any state wide victories there before 1933 in the novels, so I don't think they were that strong there.Otherwise, we don't know much about the strength of the party's in Georgia, but since it is a Deep South state, it probably favors the Whigs over the Rad Libs, so I would give it to the Whigs. That gets the Whigs up to 47 EVs.
Then there is Alabama. In the novels this state went for Featherston in a big way in the 1933 election. (It was called very early in the night.) However, Hugo Black was an Alabama boy, and he was murdered in Alabama. Thus the backlash against the Freedom Party from that killing is likely to be stronger here than in any other state. (Especially since Alabama was also the state where President Hampton was murdered.) Alabama also lacks a Freedom Party Governor at the time of the 1933 election, and there is a good chance President Mitchel declared martial law in the state following the murder of Hugo Black, which would severely curtail what the Stalwarts can do. Thus with all of those factors in mind, I think the Whigs probably pull it off here, which gets them up to 65 EVs.
As for Tennessee, on it's face, it should go Featherston. It voted Freedom Party in both 1921 and 1927, and it seems likely that it elected a Freedom Party Governor in 1929, so again the State Militia will not be keeping the Stalwarts in check. Still, this is Hull's home state, so he is probably reasonably popular here and the mountainous eastern part of the state should be strong Radical Lib territory that isn't easy for the Stalwarts to attack. It's also likely that much of the Confederate Army is stationed in Tennessee since it is right on the US border. The presence of the army should help reign in the Stalwarts somewhat. Thus lets have Tennessee end up to close to call with both Featherston and Hull claiming victory.
Thus the initial election results are the Freedom Party 91 EVs, the Whigs 65 EVs, and the Radical Liberals 47 EVs, with Tennessee undecided. With Tennessee seemingly deadlocked, it will probably fall to the Confederate Congress to decide who won the state, at which point it is easy to imagine a Radical Liberal-Whig coalition, which after considering all the evidence, is shocked, shocked to find that Hull won the state.
That leaves the final electoral count at: Freedom Party 91 EVs, the Whigs 65 EVs, and the Radical Liberals also 65 EVs. No one has a majority in the electoral college, so the election goes to the Confederate House, where the same Radical Liberal-Whig coalition that gave Tennessee to Hull, elects him as the President. (Even though the Whigs won the same number of electoral votes as the Radical Libs, the Radical Libs won more states than the Whigs did, and since the House votes by state, that puts the Radical Liberals in the better position to be the senior partner in the coalition.) Featherston is of course outraged, feeling he was robbed of his victory in Tennessee, and that he only lost Alabama due to Confederate Army bayonets, so he responds by preparing for civil war.
(Note: Even if Featherston wins Tennessee, he still doesn't have an electoral college majority in this scenario. However, that would leave the Whigs far ahead of the Rad Libs in electoral votes, which would probably mean President Longstreet rather than President Hull. Thus we either have to have Hull win Tennessee or we have to have Georgia go Rad Lib instead of Whig to make the scenario work. Given how strong the Freedom Party appears to be in Tennessee in the novels, the second option may actually be more plausible, but I thought the first option was a little more interesting, so I went with it. If we go the other way, having Featherston win Tennessee while Hull wins Georgia means that the final electoral college results are: Freedom Party 109, Radical Liberals 67, Whigs 45. Featherston is real close to a majority but didn't quite make it, so the election still goes to the Confederate House.)