I hate those damn things. Semi sealed are a bitch and a half and i hope no one ever has to deal with this struggle like me, and you are now, struggling with. I worked on these MANY times and i can give you my best help.
First off, Semi sealed can be pretty messed up from the start. The driver may need to be greased and re ball bearing'd(??)
When tightening the hub, tighten the non drive side FIRST when tightening your chain. This will help with the stupid lock nut on the driver shifting. Usually, the non drive side stays pretty nice on there. Other times you may need an all new race nut because they become deformed and useless after a while. Same thing with that driver. What it probably is is those race nuts that have the ball bearings sit on them, they just break and make it impossible for them to roll smoothly. Also, if you need a new sealed bearing, you're completely fucked. It doesnt come off the axle and it sucks a lot. You either need a new axle or hub if thats the case. Also, be sure there isnt a shit ton of grease on the driver part because that can cause trouble too.
When tensioning the lock nuts it is best to just basically finger tighten them then nudge them slightly with the wrench and hope that is the right way.
Good luck dude.
Also, if youre lucky, some dudes on here in the for sale section have real cheap and better quality rear wheels for sale. SO get shoveling snow, raking leaves, or mowing grass. Or get a job and enjoy the new rear wheel you have! haha
I hope it all works out. Oh and Bike shops are a GREAT place to have fix these things. if you have one locally, they could probably help you for like 25$
References: OneGuyIlluminatiEye, robinson79, Brian Griffin, The Horror Contact, StoreBoughtChild, C_Johnsonbmx, dkTechEthan, etc.