Make sure to disable Windows hybrid sleep. If your system isn’t shutdown properly and you access the Windows partition from another system that can destroy data.
If you just want to keep the data on the Windows partition and usually don’t need to run Windows, I’d remove the Windows drive and keep it somewhere safe, and get another SSD for Linux. That way, the two systems are completely separate and can do nothing to each other.
Swap is mostly a crutch for too little RAM, if the system doesn’t have enough the best solution would be an upgrade. If that’s not possible, consider zram-swap, or if you have to, swap to an SSD (that will reduce its lifespan, though maybe not in a relevant manner). If you swap to an old HDD you won’t have much fun using the system.
You’ll probably have to work alone until you have a compelling proof of concept / vertical slice that might attract contributors - but it might not, and then you’ll have to continue alone. Also, open source and gamedev isn’t the best match (depending of the type of game), since testing games is tedious boredom that won’t attract volunteers, and developing a story in the open removes any surprises.