You are looking at it from a post war perspective and concentrating on '44 and '45. Yes the Allies had enough capabilities to fight two essentially seperate wars. And Midway defeat, or even a Japan MAX situation (USN PACFLT capital ships all destroyed, carrier raids on the West coast, an unlikely but still plasufible senario) would only extend the war by 6-18 months at best.
But, we are looking at '42. For most of that year the massive Armies, Navies, Air Forces and support infrastuture were orders on paper. We historically saw BOTH the British Empire and the Americans shifting or diverting assets to the Pacific when that blew up. And it having major affects on ETO and Med ops, just see N Africa as an example. In 1942 for most of the year the combined chief didn't think of theatres of war and assets to be sent, they thought about a global war and sending troops wherever they were needed. Chiefly because they did not as yet have resources needed to fight everywhere without going on the defensive or abandoing plans elsewhere.
To a General saying "
don't worry, in 6-9 months you'll have enough men and material to do whatever you want, no need to shift" is not going to be a persuasive arguement when he feels he needs them in 3*.
So yeah, the Generals and political leadership of 1942 is going to be super conservative. They are going to go deep into stabalization mode in the Pacific and thats absolutley going to affect Pacific Operations as assets are transferred or diverted.
For the ETO and Med this means Torch is errr
torched. Instead we get the original plan of an American division or two reinforcing Eight Army in Egypt. No Torch means that Rommel does not withraew 1500 miles to Tunisa he did in OTL, instead he is going to dig in in Libiya. Reinforcements from France do start coming in (plans for that pre-dated El Alamein). When the situation stabalizes then probbaly a Torch like landing, in April/May of '43. Which means a collapse in N Africa in July or August (no consilidation we saw in OTL), Sicily in October and mainland Italy landing in December or January of '44. Admittedly, for the ETO at this point ATL and OTL merge.
As far as the Pacific is concerned, it means the USN is going be unable to protect the US coast and Australia at the same time, which means the RN has to take over the latter. It also means that the RN keeps large ships East of Suez instead of returning to the Med as they did in OTL '43. Probably start offensives in '43 in the Bay of Bengal and the Malayan peninsula from Ceylon and the Eastern Seaboard of British India, which IOTL, Churchill was oushing for. No offesive in the South or Central Pacific for at least a year.
Which means comes German capitulation, the Japanese fleet is still in being and the Allies are still far from the homeland rather than the doorstep as they were in the real '45.
*It must be noted that all Generals on all sides underestimated just how much material could be produced how quickly by industry.
No. The Interim and Taregt committees were set up in spring '45.
https://www.atomicheritage.org/history/interim-committee
They considered how best to use the bomb, and when they did, vast armadas of B-29's were bombing Japan, it was an easy enough recommendation to be made that it be against a Japanese city
The other options, which were dfiscussed in some detail OTL, will look more attactive, if heavy bomber are out of range of Japan ITTL.
LIke againt a Naval base or large military post, which was rejected (chiefly since the B-29 and the carriers had already mostly pounded
those to smithereens, both in Japan and elsewhere).
It should be remembered that when the committees met, the estimation of the yield was lower, about 1-5 KT, it was not after Trinity that they realised it would be pretty big.
Thats not too much bigger than some of the larger raids, and would make a city attck less attractive.
So war might end with the Japanese citiies mostly unharmed.