EDIT - dang... guess I am late to the party... glad you go it out! But still recommend the Wintergreen oil for screws, etc!
before you break out the C-4 or the 3/4" impact wrench - and/or break the press frame (and YES that would be ME if I were doing this...).. Go to your local pharmacy. Ask the pharmacist for a bottle of Wintergreen oil. It will not be on the shelf - if he has it it will be behind the counter (no CLUE why!). ~$6-7/4 oz bottle cpl years ago. Drip that around the threads numerous times, maybe for a week. Then try it. I had a small gun screw that Kroil wouldn't even touch. Gunsmith told me about the Wintergreen oil. I applied it 3-4 times over a week and removed the screw.
If THAT doesn't work, put press in freezer overnight. Take out, apply torch to outside of press and try loosing then.