There is no problem in sterilizing glycerol in autoclave in a glassware. For freezing, I make a solution of 70% Glycerol, autoclave it and then mix it 1:1 with the fluid present in the culture that I am going to freeze. I don't think there is going to be any change for a 10% more of glycerol.
I would suggest that when you prepare the solution of Glycerol 80%, the solvent that you use (e.g., distilled water) is from a fresh source. Certainly, you can sterilize the solution of glycerol in an autoclave, but after that you use it, then you will have to sterilize it again, because after to be in contact with the air it can be contaminated.
I faced a similar dilemma few months ago. I was told autoclaving glycerol would produce acrolein, which inhibits DNA repair. so for molecular biology purposes it is advisable to filter sterilise glycerol.