I want to remove about 5 layers of exterior latex paint from my deck, which is made of treated lumber, and then stin it with a colored stain. My plan was to use a citrus-based paint remover and pressure wash it, then go over the whole thing with a floor sander to take down the grain.

Any ideas if this will actually work? the deck boards are attached with countersunk screws, so I hope the stain covers them up.

DON'T SAND PRESSURE TREATED LUMBER!!!!!!!!!!

You can easily and safely remove the latex paint from your deck using the PEEL AWAY 7 product which is available at Sherwin Williams

as always Hy is recommending a PEEL AWAY product (hy do you work for them) any way you could use a citrus striper and you will not have to sand the wood there are strippers out there form Back to nature,Zip strip ,Kleenstrip ,Rockmiracle, and many others that will work

About using a sander -- the nail heads (or screws) in the boards will probably make that impossible.

do i use paint remover
do i use pressure washer
do i use drill hand sander