Try heating with a hot air gun on the fork leg, also try a 50-50 mix of acetone and ATF fluid. As far as the filler screws I would try removing with a screw removal bit, they come in a set and are different than Eziouts. If this doesn't work drilling the heads off the screws carefully with a counter sink drill bit could be an option. You need to keep it centred and square ( helper is handy to make sure you are drilling square) and only go deep enough to just remove the head. Hopefully with the heads and filler removed and with a bit of heat and penetrating fluid they will come out. If they don't you will have to drill them out, if you have drilled the head off and it is centred and square you could use this as a guide to centre and drill out the screws. It is a tricky and daunting task go slowly and carefully. If you are not confident try out the techniques on a bit of scrap material drill, tap and countersink, fit some screws and try drilling them out with the extractor, try countersinking and drilling and retaping. It is better to stuff up a bit of scrap than stuff up the tank.
Regards Martin