@timely It sounds like you may have an undiagnosed structural problem in your heart (guessing, and I'm not a physician) such as a valvular problem. This might explain stress-induced bradycardia and possibly hypotension after a sustained effort. Again, this is a possibility that ought to be ruled out...definitively. Or, you have a form of dysautonomia that needs figuring out. Vagal tone could be what is at play here. There are treatments for that.

It may be time to rethink your beta-blocker. They work well for incipient hypertension, mild cases, but the body can develop an intolerance to them and experience bradycardia and the associated risks for fainting, falling, being short of breath, having swelling in the extremities, even fluid in the lungs. There are other ways to bust hypertension, not just beta-blockers.

I am worried about your GERD and your physical measurements. Are you charitably overweight? Your self-described statistics of height/weight suggest you may need to consider a regimen of weight loss, something slow and manageable that doesn't make you miserable or put you in greater danger of developing problems. You must maintain motivation, and that generally means a slower, methodical, regimen of weight loss, something that can be sustained indefinitely and eventually become a habit.