In the weeks after Lincoln's murder the Congress elected in 1864 might well be in a radical mood and inclinded t0 support a radical President if he recalled it
Depends what you mean by "Radical".
If you mean willing to give Freedmen the vote without a literacy test, then maybe. But anything more than that is fantasy.
Imho, this word "Radical" can be very misleading. Most of the so called "Radical" republicans were plain simple 19th Century Liberals, ie the last people likely to go in for mass property confiscation or other vengeful measures. Note that Jefferson Davis was set free in 1867, when the Radicals were at the height of their ascendancy. Some Republicans were willing to temporarily disfranchise Rebs, but there was no appetite for treason trials.
Note also that even in the immediate aftermath of the assassination, General Grant firmly set his face against the arrest of Lee and other Confederate generals. If he can keep calm, so probably can most of Congress.