For my the next chapter in my series of dumb/basic questions, I'd like t get your thoughts on the subject of bedliner.s

My truck came with one of them, and I'm trying to decide which way to go with it: keep it on but make it better, or take it off.
The liner is not attached in any way (except for the tailgate part, which is held in place by 3 screws), because of it being loose, it rubs against the paint finish and there's some raw spots here and there. The PO put down some duck tape where the edges of the bedliner meet the top of the walls of the bed. I guess this kept the rubbing to a minimum, but some spot still got rubbed. Now that duck tape has completely disintegrated and all that's left is the dried glue residue and the fibers of the tape. I plan on going to town on that once the weather warms up a bit.

So I have few questions for you all, if you don't mind:

1. What's the best way to get rid of the glue residue and fibers? Goo-gone? WD-40? anything else?

2. Should I keep the bedliner on or not?

To be honest, I wont do a lot of hauling in this thing, mainly trips to the dump, carry the odd oversized object from point A to point B, maybe help a friend move some stuff, but it's not like this a work truck. So if I'm not going to put a lot of wear and tear on the bed, does it even make sense to keep it on?
I have a shed where I can keep it in case I ever need to put it back on before a really messy haul...

3. If I keep it on, what's the best way to attach it so it doesn't damage the paint further? Should I coat the bed with some kind of grease or silicone before putting the liner back on? Should I screw it to bed? If so, where is the best spot, on the sides of the top of the bed walls? Will this damage the body?

Thanks for any suggestions