I’d call the auto parts store and see if they can order those splined bolts for you.
As a last resort I’d get at least grade 5 hardened bolts and nuts to replace them.
I’ve also stacked two nuts on the end too, and the biggest hammer will have more imp[act without having to deform the threads.
And I agree with @Tester , to not walk away from a torch. It’s easy for those who do this daily to get away with this, but suggesting this to a rookie is looking for trouble.
The hanging strut has no side support. U hit it with hammer and it bounces. Would have helped to fashion a rear support rod that rested against frame. Or something similar.
I’d put the wheel back on with the lug nuts just snug…put a block under that tire and lower that corner enough to stabilize the strut and then give it a wack with a pretty big hammer.
The block under that wheel may give you a little more room to swing the hammer.
I think you’re on an unlucky streak. I’m a driveway diy’er and I’ve removed and replaced both my half shafts on both my Corolla and prior to that my VW Rabbit and didn’t have any of these stuck bolt problems you are encountering. There are a couple of tools that are helpful for stuff like this, like for separating ball joints, brass drifts for driving things apart. I presume you have those already.
If you already pulled the tie rod end out of the knuckle, put it back into the knuckle and snug the nut. This will stabilize the tie rod end while you work.
Some tie rods have a hex shape to a section of the tie rod to fit a wrench to. Others are just a round shaft and it helps to have a good pipe wrench holding the tie rod from turning as you try to loosen that nut. Rarely do you need heat to loosen this nut and I would be Leary to put too much heat to a tie rod anyway.
Sometimes you just need a longer wrench for leverage.
One trick is to use an open end wrench on that nut. Then using a large boxed end wrench, slip the box end over one of the jaws of the open end wrench ( the end not on the nut).
This will likely double the length of the wrenches for more leverage.