1 - I’m in south-central Pa. Tried to do a list of publicly available machines on the Shapeoko wiki: Shapeoko CNC Router, Rigid, Accurate, Reliable, and Affordable — there’s one in New York if you get to the big city
2 - Software selection is personal based on philosophy, user-interface preferences, available computer hardware and intended projects. Plexi / acrylic cutting shouldn’t be a limit though. Community-maintained list here: Shapeoko CNC Router, Rigid, Accurate, Reliable, and Affordable but I’d really suggest starting w/ Carbide Create, then trying Inkscape
3 - Please see:
where a similar query was addressed and a specific text suggested. You may find reading through the Shapeoko wiki (linked above) of interest as well — I’d be grateful to know of any topic not addressed in it, or any suggestions for improving it.
4 - Dust collection / shoe is likely a necessity. A touch plate is the biggest bang for the buck improvement, or maybe a corner finder — there’s a commercial one which integrates both, but it’s a simple enough thing to make (if one just has the tool to make up the connections). I believe Carbide 3D is working on their own.
Clamps are pretty much a necessity, but it’s easy enough to make one’s own. Fixtures are usually specific to a project — you can see one such example here: Shapeoko CNC Router, Rigid, Accurate, Reliable, and Affordable