Bathtub hot water faucet handle screw is rusted

My bathtub's hot water handle has been stripped for some time, in that I have to hold the handle at an angle to have the water turn off all the way.

I got a new set of tub faucet handles today. The trouble is, with the hot, I can't get the rusted screw off the seat. I sprayed some WD40 on there and cranked as hard as I could (with my wife holding the handle so it wouldn't turn) but it's rusted on there pretty good. Any suggestions you guys have would be greatly appreciated.

Thanks,
TJ in Pasadena, CA

Sometimes if you give it a couple of shots with the WD-40 and wait, it will come loose. Also, penetrating oil (watch you don't drip it all over and stain things). A torch sometimes will cause enough expansion (doesn't take much) to allow you to break the corrosion and get it loose. You need to be careful with the torch! as you don't want to blister the chrome or any other parts. Often the serrations on the stem are rounded off and a new handle will not resolve the problem. If the handle insides have been rounded off, then a new handle should work, if not, then it is a waste of time - you'll need to replace the valve or the stem. If you can't get the handle off, you should be able to pull the entire handle, stem off and take that to a good plumbing supply house and get a replacement stem. Then, your new handle will fit! Maybe it is time to replace it with a new pressure balance valve (and or a temperature controlled one). From an advanced hobbiest.

Craftsman makes a tool called ScrewsOut. It is a bit that bites and backs out a stuck screw.

Based on your description of having to "tweak" the handle to operate, I fear you may have bent the stem. All in all, your best shot may be to remove the stem, handle and all and replace everything.

This screw that's rusted is I'm guessing a phillips head screw. If so, it is very easy to strip the slots out. So be careful. Try this, it has worked for me on many occasions.
Hold your screwdiver firmly into the screw with some axial pressure while also applying a bit of torque.
Give the screwdriver a sharp blow with a hammer.

This may be enough to break the corrosion. Again, be careful and use some judgement as to how hard you hit it, so as not to cause damage.

On second thought , Take Jimbo's advise and replace everything. It's the best and safest way to go.