Poodleshooter. If I read you correctly, your metal is discoloring at the surface quite rapidly. Sounds to me like you may have the metal too hot. Your lead is oxidizing too fast. Fluxing will help clean the lead. I don't recommend keeping the mold hot by setting it in the flame. Just put a corner of the mold in the moltem metal for about 10 to 15 seconds. Also, use a "BIC" type lighter and smoke your mold with it. Paper matches have wax impregnated in them to help them burn which can deposit grease in minute quantities in your mold, making casting difficult.
I have not seen where a too hot mold made bad bullets though. The frost like look hasn't hurt any of my cast bullets that I can tell.
As far as that lead that did not harden properly, it may be contaminated with something. You said you were using an aluminum pot. Some of that aluminum may be melting into your lead (again too hot a melt?). My suggestion is to get rid of that pot and get a cast iron one, or invest is a Lee production pot. They aren't too bad for the money. I have one as well as a Lyman Mag pot.
It could be, and again I see too much heat as being the culprit, that your mold has gotten so hot that the sprues are taking an abnormally long time to solidify.
The more I think about it, the more I feel that too much heat is what is causing your problems.
Let me know if this solves the problem. If not, we'll have to check out the contamination angle.