Which Amplifier Should I Use After my DAC (what are I am doing wrong)?
You should put a series capacitor between the output of you DAC and the input of your amplifier.

It looks to me that the problem you're seeing results from the amplifier doing its job on the DC component of the signal as well at the AC component.
Having the capacitor in there will block the DC, but allow the AC to pass through.

Off the top of my head I'd guess that a value of a few uF would be sufficient.