1) Check out Sharon Shamber's method of sandwiching using a table top (kitchen table will do), and two boards. You don't need a whole lot of space, you won't get any ripples or puckers, and it's EASY. I'm at work and can't look for the link to the video - but do a search on her name and basting and you'll find the video. It's fantastic!!
2) Yes you can do the squares first starting with the center squares and working your way out, then then sashing, then the borders.
3) BEFORE YOU START ... make sure you practice practice practice FMQ on scrap. I am assuming from the beginning of your post where you said you thought you could handle a wall hanging that you are not comfortable with FMQ yet. So if not ... take the time to practice every stitch you plan on putting onto the quilt. Use the same fabric weight, the same thread, and the same batting. Work out all of the tension issues and anything else that could come up. Can't coun't how many threads we've seen on QB lately that began with "I'm FMQ'ing a quilt and it's not going well". So make sure things go well BEFORE you put your quilt under the machine.
Edit - aha! I see now that Feline put up a link to the video.
Good luck!! And have fun!!