with fish and smaller animals I usually let the pile "cook" for a month then turn it every other day after that until its cold and the materials are unrecognizable. Make sure your pile is large enough....mine are about 5 feet high and 5 feet wide.
I have composted fish and its turns out just fine. Once the pile gets hot they disappear within a couple of days. I have also done this with roadkill deer, foxes, birds, squirrels, and rabbits. There is no smell whatsoever and i never had a issue with critters. With fish you could also make homemade fish emulsion or just do it the indian way and bury it in holes during planting time.
Use roadkill....they are just bags of fertilizer laying all along our roads ripe for the taking...killed accidentally and waiting for someone to give them a proper burial
there is a design for a earthship hut....its much smaller and round. It doesn't have a greenhouse but it does collect rainwater and its earth sheltered. Cost is around $2500 USD to build so very cheap. You might want to try that first before doing a whole one plus you will gain some experience on how to build them. Only downside is that they don't stay as warm as an earthship with a greenhouse. Still the lowest the temp will go inside the hut is that of the earth around 55 degrees or so.