Frustrated...Seeking advice/reaffirmation (long)

I am in search of advice and/or reaffirmation that I am approaching this the correct way. Last August I began to swim regularly. I swam in high school 30+ years ago, but my technique was never very good - more on that below. I don’t swim with a masters or other group as those nearby have schedules that are not conducive to my personal situation (I need to swim very early in the AM). I followed a One Mile Program outlined here, and by the end of September I was swimming 2000m per day. Through the beginning of February, I swam 2-4 times a week at least 2000m each day - one day would be 2000m straight and the other days would be 2000m in interval sets (pyramid or ladder). The idea of swimming in an open water event has interested me for some time (even before August). In February, I made the decision to look into possible events and determine what I needed to do to prepare. I am thinking the 1000m Pass-a-Grill Challenge would be a good first attempt, and I figured I would try out this local lake swim as well. As I said, my technique is poor. I breath every other stroke and only on the left, and I begin my pull way too early. In fact, I found that I was using the leverage from my right pull to lift my head to the left to breath. After a swim, my right arm shoulder was noticeably more fatigued than the left - I worked that side harder. I figured that to swim an event I needed to increase my distance in practice and I was concerned my poor form would lead to a shoulder injury. So I decided to see if I could find some lessons. So, I signed up for weekly lessons at the YMCA, and have had 3 thus far. The instructor immediately had me working on rotation drills and catch up drills. She introduced me to bilateral breathing every third stroke, or least attempting to. When I work with her, she tinkers with my stroke and seems to think I am getting it. She encourages me to practice the drill on my own, which I do - I swim at least 4 times (if mot more) on my own between each lesson. I can “visualize” what I am supposed to be doing (or at least I think I can), but when I swim alone, everything falls apart. I just cannot seem to keep my non-pulling/recovering arm straight. Seemingly on its own accord it bends and begins to pull way too early and/or it puched straight down and tries to leverage my head out of the water to breath. Everything happens so quick, that I cannot concentrate on of all of the different things that are going on - arm position during pull, arm position during recovery, reaching, rotation, breathing - and it all just collapses and I am gasping for air! I really feel like I am just flailing around. Also, my endurance (such as it was) is totally gone. I had thought that I would start the One-Mile Program at the beginning swimming with the new techniques that I have been practicing (doing some kicking and rotational drills beforehand and including some drills (such as a catch-up drill) in the sets). Well, again everything falls apart and I cannot even finish the first set of 100s. I can handle the bilateral breathing for 25 -50m, but then I can’t catch my breath and I immediately start my pull too early and lift to breath rather than rotate, and generally flail around. At this point, I am thinking that I need to table my open water goal. I don’t see how this is going to come together anytime soon. The ironic thing is, 4 weeks ago I was swimming 2000m in a 25m pool without a break - took me about 40 minutes. Now I stink. Am I expecting too much? I am becoming so frustrated! Is the answer to keep flailing and it will eventually come to me?