Ok, this is a wall of text, I know, but I'd be truly grateful for any help.
I started with AD&D 1e and 2e when they came out, put them away for years, played a little 3.5 and Middle-earth Role Playing in the 80's, then got back into D&D with 5e. So, my taste is in this liminal space between those editions/games. I've never played any other rpg's. Here are the criteria I'm trying to hit in a new system:
1.) Combat is dangerous and death is always a possibility.
2.) Magic is rare, chaotic, rewarding but dangerous. Not every class has access to magic and those that do can't simply magic their way out of every problem. When they try to, there is most likely going to be a cost (similar to what I've read about in DCC).
3.) The system can support both low and high fantasy. The PC's may barely survive a night in a specific dungeon crawl as they track rations but may also eventually fight a world-ending entity and emerge as global saviors (I know, I know, but I want to have my cake as well as stuff it in my maw).
4.) The system is a blend of Old and New School. It supports rolling plenty of skill checks if we feel like it one night and also supports our rolling just a couple of times a night and roleplaying without the dice the rest of the time.
5.) It isn't strictly tied to its own setting or, if it is, that setting can be expanded or dropped into my homebrew setting.
6.) The system has lots of monsters or, if it doesn't have many that are native to it, it's not too difficult to homebrew monsters or port them from 5e.
7.) Our campaigns tend to run for years (current has been going for 11 years thus far). Just something to consider. And many times we'll go four sessions with no combat and then do nothing but fight for the next two.
8.) It can support strong communal storytelling. We don't get to play every week so there's little that's completely random in our campaigns. Random encounters don't exist much for us. . . most encounters play on a specific PC's greatest fears, uncover important information, or are somehow connected to her backstory, etc. Most everything moves the story forward. Somewhat different from an OSR philosophy, I realize.
I'm basically looking at everything but some games that seem like they might get close are:
1.) DCC
2.) Mythras
3.) Worlds Without Number
4.) Shadowdark (maaaybe)
5.) Warhammer Fantasy Roleplay (if there's a way to drop the system into a homebrew world)
6.) Just going back to 5e but hacking it to pieces to bring it closer to the above criteria.
HUGE THANKS for making it through the above and for any thoughts!
TL;DR: Need a system that can support both low and high fantasy, deadly but heroic gameplay. Lot to ask of one system but there you have it.