I agree with what everybody else has said. Most important thing is to not become too obsessive with it though. I took a vacation for 10 days this summer and I didn't workout once (wanted to do all I could while traveling, so that was the focus for my time). I don't feel like I lost too much.
A...
great for lunge related moves. outside of that I prefer dumbbells. You can find groups that workout exclusively with them like crossfitters. I use them in a few different ways throughout the week.
I feel like I've read a lot that weighs in one way or the other on this. I personally do fasts for religious reasons occasionally, but that falls on a rest day. Any day I train I eat before and after for fuel and recovery personally, but like I said there are lots of people who advocate one way...
My current program I'm trying recommends various things of either 8, 10, 12 sets to failure. With that in mind, if you're not in it that day then what the weight is that is to failure should also adjust. Not the end of the world or some kind of regression by any means. Just means you're not 100%...
I've also got a jacked up shoulder. Rehab has had me do stuff with resistance bands. I just switched to those full time for upper body till it's healed better and I can resume normal routines.
Research any of them really well and start light. If ever you didn't want to screw up form it would be with neck stuff. A jacked up neck isn't something you'll shrug off like other things.