Really seems time to just accept your hardware limits that system to use of 32bit software. Shuffling components around, things like hdd's-etc is clearly not going to accomplish anything, it's just needless hassle and risk. Something gets damaged, incorrectly reinstalled or static discharge zaps something you'd prefer remains unzapped. All this time, effort and x-risk for zero real gain. Nothing you or anyone else can do is going to get around hardware limitations. Minecraft isnt the only thing in the world and thanks to Debian gnu/Linux that system can go on being a useful piece of equipment for a long time to come. Amazing in/of itself, a 15yr old PC can still be made to run well in 2020.

Ps, also doubt you're the only person ever, who wanted to use Minecraft servers on 32b, if you're going to dump more time into this would start googling on that angle see if somebody has already posted work-arounds online. Ah either way, good luck. You dang sure get A for effort.