Star Wars

1. I’ve never heard of a “check” in star wars lore, so can’t help much here. There are “Banking Clans”, so obviously there must be some equivalent to checks and wire transfers, but it doesn’t seem common for the average joe. A google on Bounty Hunters mentions a “Transfer Register” associated with the bounty hunter guild, but it’s a one off reference. Most people operate with credits or other hard currencies, the nature of the setting strikes me as “bank accounts are for the wealthy”.

2. When I hear LOTR in space, my mind goes to Kyber Crystals, specifically being sourced by the Empire to power the Death Star - assuming you’re looking for that specific “hide the macguffin from the evil overlord until it can be forever removed from their grasp”. If you’re looking for proper large scale battles, you’d probably have to stick with the Clone Wars for a “modernish” setting, though it’s never hard to find an excuse for reasonably sized skirmishes to occur wherever you choose.

I’m unsure when the canonical start of the hunt for Kyber Crystals for the death star was, but the death star itself was initially being constructed around Geonosis during the clone wars so it’s perfectly reasonable.

3. We see dark side Soresu from Darth Bane and Zannah, a little older than your intended setting but still a useful example. Zannah in particular was never a particularly offensively powerful duelist, so Bane taught her Soresu to compensate(it’s been a while since I’ve read the books, so I’m more or less summarizing the wookiepedia here).

With Obi Wan, I would reckon between abandoning the principles of the Jedi Code and not lacking the physical strength to pursue offensive forms, he would move away from Soresu, but due to his innate lack of aggression, choose form 6. Rather than switching all out to hyper aggression, I’d imagine Obi simply choosing a more balanced approach - instead of being the perfect defensive duelist, and always attempting diplomacy and negotiations, he becomes much more willing to use swift applications of violence to resolve otherwise complicated situations. I would imagine his fall centering around more of cynicism and disenfranchisement rather than hatred.

I’m sure he’d still be an excellent defensive duelist, but I think a fallen Obi is a weaker duelist overall - he’s the perfect Soresu master because he’s everything the Jedi code strived to be. Take that away, and I don’t see him using the gifts of the dark side well enough to offset the loss of balance.

For the LOTR portion consider Dathomir: Force witches riding rancors not far off from Nazgul

What from lotr are you trying to emulate?