Tips for improving stroke imbalance while swimming

Hi community, I'm wondering if I could solicit some help with a specific problem I've been having while trying to learn to swim for distance. My goal is to do a sprint triathlon in May of 2019. I took swimming lessons this year to get the fundamental down, and now swim 2-3 times per week. I'm at the point where I can swim in bouts of 25-50 yards, but then have to stop to rest. I could probably swim 400 yds as long as I was floating on my back for some portion of that to recover. I'm in pretty ok non-swimming shape and believe that my problems are at least equally form related as they are fitness related.

One of the main issues I've noticed is that my form struggles whenever I breathe while stroking with my left arm (with the left side of my body towards the bottom of the pool). It's hard to really get that breath, because my body starts to sink. In fact, it is generally easier to swim when I breathe every 4 strokes instead of 3 and only breathe on my stronger side. But this is a long time to take a breath.

My left arm is kind of worthless. During the active phase of the stroke it has a tendency to swing out away from my body, I guess to avoid doing any work. I've tried to correct this only by being attentive to how it is moving through the water, which helps somewhat but when I am no longer attentive to it it starts to cheat again, the traitor.

I'm sure these two issues are related. I'm wondering if there are specific drills that anyone knows of that might help me to address this issue. Thanks in advance!
Jordan