The marks on the back look easy to fix - just a little bit of varnish. If they don't go all the way down to the wood, it's not even something there's any hurry for, except for your peace of mind.

I can't comment on the bow holders - I'm not good at that kind of thing.

The humidity issue.... that's going to be a bit tricky.  What messes up violins more than anything else is rapid changes in temperature and humidity, and a few months ago, I would have said that that's not enough variation to matter.

But we had a discussion about that subject a couple of weeks ago, and a luthier suggested 40%-60% as the ideal range,  and some other people commented that above 60%, there starts being a significant chance of mold growing.

The box and the clothes aren't going to help, I'm afraid.  If the air in the room is at 75% (to pick a number), then when you open the case, the inside of the case will very soon be at 75%. It would also get to 75% inside the case even if the case were shut and covered with other things, unless those other things were better than airtight.  (Water molecules are smaller than air molecules.)

Keeping a violin closed up in a case (or a case plus other stuff) is only helpful for slowing down the transition to a new temperature or humidity. It won't (by itself) keep the humidity (or temperature, for that matter) in the desired range for long periods.

One possibility would be something like this: ie=UTF8&qid=1517614672&sr=8-4  

I use it for my hearing aids. You'd have to poke some holes in the lid and keep it inside your case, and then keep the violin inside the case any time you weren't playing it. One thing I like about it is that it has mostly white beads and some blue ones. When the blue ones fade to grey or white, they need to be "recharged". You recharged them by putting them in an oven  (110-120 C would probably do it) on a wide pan, and let the high heat dry them out. You then pour them back in the bottle and they're ready to go again.

There are some problems with that method, though. They're designed to deal with small quantities of air and moisture. With the bottle sealed, they last for several months before they need to be recharged. I don't know how long they'd last in a case. If it was as little as a day, you'd need at least two, and it'd be a fair amount of work.

There's a second problem - every time you take the violin out to play, you're changing the humidity it experiences fairly drastically, fairly suddenly. I don't know enough about the subject to predict what would happen, or even to say which would be worse - constant high humidity or frequent rapid changes.

I'm assuming you don't have air conditioning, because air conditioners tend to keep the air at a pretty constant humidity. (And lower than 85%. It might get as high as 70%.)

A cheaper variant on that idea would be a dehumidifier.  That will probably be some work to take care of, also, and probably be somewhat noisy, but if you have one room you can use for practice that can be mostly sealed off (so that the air and humidity flow in and out of that room is limited), that might be an affordable solution. You wouldn't need to keep it in the case at all if that would work.

Finally, since (as far as I know) the main danger from higher humidity like that is mold, maybe something to control mold would be the answer.

I'd recommend trying to find luthiers and players who live in Colombia and ask them what they do. (And hope they don't give you nothing but answers you can't afford.)