Western blot transfer issues
The first thing that comes to mind for me is that the transfer seems excessive... isn't histone sub-20 kDa? I have often transferred similar-sized proteins at 4C for 30 min, 30V. 

In general, presence of SDS will inhibit transfer efficiency, and increasing alcohol in your TG buffer will counteract the effect of SDS present. Perhaps bring down the methanol to 10%? I would be curious to see that reference regarding the SDS/pre-equilibration, though. That certainly runs contrary to how I understand it working. (Note: I flip-flop between equilibrating or not equilibrated my gels without any observable differences.)

If your acrylamide or ACS had gone bad, your gel wouldn't set.

If you don't already, I'd suggest running a Bradford or BCA on your samples to be sure that you're loading the same amount into each well. Having loaded more into each well could give the appearance of uneven transfer.

To be honest, I don't really see what you mean by uneven transfer, based off the Coomassie and Ponceau. If you're seeing a gradient effect across a large portion of the gel, I would suggest you visually inspect to make sure that the gels you cast are even width all the way across. Having a thicker gel in one place than in another could impact the resistance (heat) in that part of the gel and impact transfer. If you're seeing a lane-by-lane transfer efficiency shift, I would suggest localized pH or temperature changes due to uneven loading of salts, protein concentration, or lipid concentration.

Hope this helps!