I am also a martial artist, with no cash for a weight room, in the summer. During the school year my university has a weight room, that is free for students. This has forced me to become the macguyver of excercise. What you need is a good back pack, a weigh scale, and a bunch of heavy stuff (books, and weight plates work best).
So when you do body weight excercises use the back pack for extra weight, in addition use unilateral excercises like pistols, one arm pushups, before you add weight.
You can also wear the back pack, for chinups, place it on your pelvis for bridges, the only ecercise it is not good for is handstand pushups. Using the weigh scale to find out how heavy the back pack is allows you to quantify your progress, and allow you to wrk very close to your 1rm. If you want to work your abs go for one of those cheap 10$ ab wheels, they work great. if not an you have acces to a bar you can use for chinups, wear the pack and hang upside down from the bar and do full situps untill your nose touches your knees.
You can also use the straps of the back pack and use it like a kettle bell, so you can do bicep cruls, one arm snatches ect. Hope this helps, but if you are 275 lbs at 6'1 You can build qiute a bit of strenght and muscle just using body weight excercise, just pick the right ones. Your best friends are the 1arm push up, and the pistol.