Hi, and welcome to KnittingHelp. I'm glad you found the forum also. There are lots of people here to help.
Mostly the answer to your questions is yes. You have the right idea about finishing the neckline for this sweater.
The ends of the neckline bind off are going to be the beginning and end of the row. It's where you'll turn to knit or purl back. Count each row separately. So a knit row counts as a row and a purl row as another.
Yes, continue the decreases for the raglan as you do the bind off for the neck. I don't think you want a pause or jog in the decreases just because of the neckline. Keep the line of decreases going. You can always make these kinds of changes and if it doesn't look right, just rip it out.
You could stitch the little gap closed with a tapistry needle and a short length of your yarn but really, it's better to ignore it for now. When you pick up sts for the neckline, be sure to close the gap (don't pick up a st in the gap). If that doesn't fix it, close it up then with the tapistry needle and yarn.
Good luck finishing up. Come back with more questions if needed and post a picture of the finished sweater if you can.