It can be frozen yeah. Good luck.
Air bubble? I think air bubble is not safe for administeration. If air bubble goes into your veins, then it can stop your heartbeat in an instant. Also, I think there is no problem with mixing two different peptides. After all, there are blended or mixed peptides being sold in the market.
Yes, you can do that. You can mix the two in one syringe and freeze it. It should not degrade your peptides. Go for it! Don't let uncertainties hold you back because it is perfectly fine to do that.