Newbie given older (outdated?), sump, skimmer

[Dweezilz]

Sorry for this long post!! I'm venturing into my first saltwater tank (besides my brackish Opae Ula shrimp tank) with my 14 year old son. We want to start really simple so plan for fish only with dry-rock / life (not live) rock. We were 'gifted' a 75g tank and 30g home made sump by a neighbor who moved out 12 years ago! I never saw the tank setup. He also gave an external Berlin Red Sea XL and a wet/dry box he hadn't used for many years. They have been sitting in my basement since then. Assuming it still holds water, I need some help. I've done a ton of reading the last few weeks, but three items (for now) are difficult to find answers for and I'd love to get some help.

1. The sump is a 30g tank (36 x 13 x 16) with three sections (see photos). S1 is 12" with 8", 7", 8" bubble trap after it. S2 is 16", then a 5.5" divider to the S3 which is 6". The problem I see is that the dividers are too short I think. For the refugium to go in the 16" area, it means the water level can only be 5.5" max before it trickles over to the return area (6" wide). The protein skimmer has to go in the 12" area I'd imagine. Do I need to rip out the short dividers and add new ones? Are all dividers too short? Can I add on to the current dividers to make them taller? Or forget the sump totally since we want to start out simple?

2. Since the Berlin is really old and I'd need to get a pump for it since it wasn't included (no pumps were), I think getting a new in-sump skimmer is best. The Berlin won't fit under the tank anyway and for now, I do not intend to run anything to my basement as I want to start simple. Is it a good move to not use the Berlin? I also don't intend to use the wet/dry as it won't fit under the tank either, however I could build something to hide it next to the tank I suppose. Should I scrap the sump and skimmer and just buy a hang-on all in one filter/skimmer?

3. This is the most difficult issue. The tank (see photos) has two built in overflows (I think they are overflows) which are small (6x3.5), one in each corner of the back. They only have 1 drilled hole each. I do not want to try to drill more on my own. They don't even have anything to prevent fish or snails from falling in. No clue at all what to do with them. I read up on the 3 overflow methods but these don't seem conducive to any of those. I do not want to risk a flood in my familyroom either which scares me with this setup.
Do I just mount the returns next to overflows?

This all makes me think I should just scrap the sump & overflows and simply get an all in one filter/skimmer and hang it on the back.

Thanks in advance for any help!! I'm trying to learn on the fly!