To get the FW off, you need the Park tool and a wrench that opens to 1". A 12" crescent should work if you don't have a 1" .
Suggest you install the tool, reinstall the skewer to help hold remover in place and keep it lined up straight. Snug it up then back it off a turn. Loosen FW slightly, back off skewer 1 more turn, repeat. By then, the FW should be able to be spun off by hand.

Get a 6-8 speed HG compatible chain. I'd stay away from the X-mart chains, but otherwise most anything should be fine.
Set chain length-
Loop over the largest Ring & cog without running through the RDER.
Allow at least 1" (2 links) but less than 2" (4 links) excess. It has to be in 1" increments, since you have an inner & outer link.
The chain has NOTHING to do with your shifters. DER's do!