Wow you even had a transthoracic echocardiogram. You are indeed all good fortunately, but I still think you are probably very deconditioned then - you also were not lying when you said you were a bit overweight. I think some cardio/exercise would do you lots of good - whatever kind of exercise you can get really. Biking, elliptical (my favorite), alternating between walking and running, or swimming. Every exercise you can do will contribute to fat loss, and the more muscle you have the more energy you will burn even just strolling around so don't leave out exercises like squats if you can do them.
If there are exercises you can't do, trust me when I say I completely understand - my advice would be do the best you can to find exercises that you can do and focus on those. But I'll recommend some options here. Between Dumbbells and you're own body weight you should be able to do all of these (and learn how to do them or find alternate exercises for these muscle groups online)
Front delt lift, middle delt lift, if you can find a cable machine do the rear delt too, bicep curl, push-ups will help hit tricep but a tricep press down machine is nice, for some serratus anterior is important to work on but you can get this one in there a bit with push ups too, planks are important though what you do with your low back you need to be careful about, you want to feel it coming from your core but some people also put a tiny bit of good curve in their backs and feel it in their paraspinals (look up what lordosis looks like - it's a teensy tiny bit of that sort of curve) but the safest way is just to tighten your core and suck it in like you're trying to lift your balls up out of cold water (check in the mirror to find the muscles that you can lift your balls up with, this is your pelvic floor and it's important to activate it when you're in a plank, it's also known as a TA brace but it's not necessarily just trying stop the flow of pee, it's more sucking in), side planks if you can, a hip abductor leg raise lying on your side, bridges to help hit glutes and paraspinals as well as hamstrings, squats (it's okay if you don't go very deep or if you need to hold on to something), toe presses as if you were jumping rope but weren't actually lifting off the ground, a lat pull down if you can find a machine, once you get enough weight off and get strong enough pull-ups, and then for forward head posture and neck pain I do chintuck and an exercise that has helped me loads where you lie on your stomache with your head over the side of a bed or something facing the ground, and you retract your chin as if you were trying to make the back of your head touch the ceiling. You should feel it in the back of your neck, kind of where your head meets your neck.
So for any of these there are probably good alternate exercises, such as instead of squats a wall sit, but I hope you'll do what you can even if it's just slow jogging, but you must challenge yourself. I would expect to be sore for 2-3 days in some cases but I would aim for being sore for 1-2 days. It was very common for me to have s lot more issues the day after I went hard on cardio.
If you don't eat too many carbs/fats but still eat protein you will start losing weight one way or another. I probably wouldn't let your carbs drop below 30g a day and I would try to keep your protein above 100g a day, especially if you've been working out. Whey protein is great in my opinion.
Fat is known as adipose tissue and it essentially participates in the body's signaling systems, it is known that adipose tissue produces inflammation in the form of signaling molecules such as tumor necrosis factor alpha. I think it's important to minimize inflammation.
I wish you luck.... Don't give up on exercise if you don't notice a difference in 30 days or whatever, it's going to take a couple months, but if you work at it and watch your diet you will see progress, and once you see progress in the form of feeling better and stronger and losing weight, you will be more motivated to workout.
