I think the forum member replies have given you all the remote help which can be provided.
I agree with Woodnthings, it may be time to seek help.
Your screws are likely very similar or the same as in my DeWalt 735 planer. The rounded head are not designed to be gripped with Vise Grips.
If the hex hole is rounded, there are few options, and these have been mentioned in earlier replies.
a) Use an extractor, which may require carefully drilling the relevant size hole.
b) Use a Dremel type tool to grind a slot for a straight blade screwdriver.
c) Use a Dremel type tool to grind off the head and then hope you can gripe the remaining stump with Vise Grips to remove. This option would also allow access with some rust penetrant. It is possible some rust on the threads was the reason the screws were difficult to remove in the first place.
We all understand your frustration. I expect most of us have had to deal with stuck hardware at some time. I have certainly had my share, especially with hand plane restoration where rust is common.