Stuck deck screw in my kick scooters

Not a bike, but lots of folks here seem to be mechanically inclined. I'm trying to turn three damaged Xootrs into one working scooter, and I'm stymied by stuck deck screws. If you don't know what a Xootr is, they are here.

I don't know the proper term for the stuck piece -- I can take a photo if it matters. It's a hex screw or bolt that goes all the way through the deck and is (obviously) flush with the deck. I've tried tapping them, using Liquid Wrench, and applying hot and cold (to the extent possible using common household items). They are stuck tight.

I really don't want to toss these lovely decks, I very much need a "guest" scooter, and would appreciate any advice.

Pam

You probably already tried this... but

Get a bigger lever arm? A longer allen wrench or a pipe that you can slip over the end of your allen wrench so you can get more leverage... I'd say put the decks against a wall, brace your feet against the edge, and then apply leverage. Pushing against it with your feet when you pull back with your arms/back might help.

Try one of those screw removal bits that you put on a power drill?

Is it a screw or a bolt? What is it holding in place? Would it be possible to just do "whatever it takes" to get it out of there and then re-tap the hole for a larger fastener?

If it's an Allen head, then a socket will give you a lot more stability and leverage than a hex key. If it's a hex head bolt, then are you saying the nut is frozen? Can you get an angle to saw/file off the nut? Got a friend with a pneumatic driver?