I think Wallace has "rage syndrome"

[Giselle]

If you're really uncertain about this, again, contact a behaviorist.

Understanding and training come before medication. And, I hate to say it, but maybe you are seeing him too much through your own personal, emotional bias. Maybe you can set up a relationship with a behaviorist and have them observe your dog over a period of time. If a second pair of eyes also sees something wrong with Wallace, then, by all means start behavioral mod. and drugs. If the behaviorist sees little wrong, then just try not to let your emotions color your judgment too much

Also, to narrow down Wallace's triggers, I highly suggest looking at this pictorial:
http://www.diamondsintheruff.com/
This clearly demonstrates that dog body language is MUCH more than ears, teeth, and tail. Once you understand dog body language well, you can start applying it to Wallace and that will help you in determining at what point he starts to aggress. Then, write it in a journal and try to find some pattern (sometimes they're really esoteric, but they're there!).

[K9soul]

Has he ever had this thyroid checked? Thyroid problems can cause really weird behavioral issues at times, and when you mentioned he seems to sleep too much and display some depressive behaviors, I started wondering about it. If it hasn't been checked before, it may definitely be something worth ruling out.