Old adage: "When you find yourself in a hole, stop digging." Until you can get a handle on what the market demands in the way of breeds and what the market will bear in the way of price, stop hatching anymore eggs. In particular, stop hatching the mixes. It sounds to me like you want this to be a business for you. If so, I suggest you specialize in just a few of your absolute favorite breeds and make sure that you keep your breeding stock separated so you don't end up with mutts.
Given your somewhat remote geographic location, I think you'd be better off only selling fertile eggs for hatching or selling straight-run day-old chicks so you can ship them. That way you don't have to be limited by the low demand in your local market.
As to your current situation....cut your losses. Keep your best breeding prospects and then do whatever you must do to get rid of the rest. The longer you keep them, the more unprofitable they'll become. On the mixed breeds in particular, reduce your price, take them to auction, give away the roos, or send what's suitable for your table to freezer camp. Once you have your flock down to a size that's not overwhelming, you can breathe a little and put some time into research and planning for a better breeding, hatching, and business plan.
Just my 2 cents....