Some years back I had a similar situation that had an unexpected result. I was able to find a rather unique/unorthodox solution. I am also a lefty and I had some serious heel spur pain on my right foot.
I had been primarily using a 1-handed BH at the time and discovered that I was developing
tennis elbow and could not figure out why at first. After 2-3 weeks of elbow pain it occurred to me that the TE was a direct result of my right foot heel spurs. Because of the heel pain I was not driving off my back (right) foot very much to hit my BH shots. This meant that I was relying on my elbow & arm too much to initiate & generate the power on my 1-handed BHs. I suppose this would have been less stress on the left elbow if I had been using a 2-hander, but I did not have a very reliable 2-handed BH at the time.
Once I realized the issue I tried to develop a reliable 2-handed BH but it was just a bit too erratic (and still is not my best stroke these days). However, another solution presented itself to me. I had been watching Marat Safin hitting
mule-kick BHs (see video link below). Even tho' his BH is a 2-handed stroke, I saw something in the mule-kick versions that I could adapt for my 1-handed BH. I would
lean a bit
forward into the incoming ball and
drive off the front leg instead of driving off the back leg.
Note: I did not employ a jump on my adaptation as Safin does on his mule-kick BH. This unorthodox solution worked quite well for me. The TE subsided and, eventually, the right heel pain diminished in severity. Following is the Safin mule-kick BH from whence I derived my front-leg-drive 1-hander:
Marat Safin jumping backhand groundstroke
.