Been there also on that rusty stuff.
For oil soak I use a recipe 50/50 mix of acetone and ATF.
A rule of thumb I use at first to use the heat/cool method and not ruin or overheat external stuff is stop heating when you spit on it and it spits back.
I've used grinders and cut the pulley down close to the crank. I have also got into such on electric motors that needed the bearing replaced and had stuck pulleys. I've got a set of SK 3/8 drive allen wrenchs that re handy for the heat cool method. (can peck on the 3/8 drive to loosen rust) Have to keep a heads up also, sometimes I find two allen screws stacked in a pulley.
On them old Troy Bilt type tillers with a rusted to axle wheel hub and similar stuff a method that I use to save all is, I've had to weld a big nut onto the end of the hub (nut/bolt is little smaller than the axle) then use the big bolt pushing against the end of the axle while heating the hub from behind. I just leave the welded on nut and paint the rim and the welded on nut is not noticeable.
Another fun one is the pulley assembly rusted onto the vertical shaft engine's PTO shaft on the MTD/Crapsman riding lawn mowers. (pulley assembly has to come off before the engine can be lifted off the frame) I've had some that I turned the complete mower /tractor on it side after removing the battery, gas, etc so as to sacrifice the pulley assembly during the removal.
Also seen some hard to pull flywheels.
A guy will acquire a feel for such stuff. I've seen people immediately ruin and break their tools and pullers, plus the assembly that could have been easily removed if they had a clue.
I've also had to let them rest for few days before continuing.
Patience is your friend when doing such.