My husband runs a lot. Weight loss used to be easy for him, but it isn't a cinch any more. He thinks that over time, his metabolism has just gotten less efficient compared to the way it was when he was in his teens or 20s. This means that although he gets a pretty constant amount of exercise, if he breaks his diet rules, he sees it on the scales.
You might also have reached the point where you need to stick with the better food rules all the time, with no ignoring them on weekends and the like, especially since some forms of exercise are now ruled out for you. If you eat as though you are burning as much energy as before, you can't help but gain weight.
Also, if you have seen "oft-quoted" that you should eat 1 gram of protein per pound of body weight every day, you've been reading the wrong sources.
Here's the formula for an average sedentary person:
0.8 grams of protein per kilogram of body weight, or
0.36 grams per pound
(Source: Dietary Reference Intake report for macronutrients)
Given that you are active at the gym you could up that a bit, but don't try to get 200 grams a day! More like 60-75.
Weight loss for tall people is the same as it is for short people. I, typically, recommend that you check with your doctor to make sure you don't have any medical issues that can affect metabolism and/or cause weight gain. 2 of those are hypothyroidism and/or Type 2 Diabetes.
If you have medical issues, they need to be dealt with; if you don't, losing weight is pretty straight forward (though not always easy). It would seem that you're getting plenty of exercise, in spite of not being able to do some things. In that case, I'd agree with AnnieBrook that you might not be able to ignore your dieting rules, even on weekends. Or if you feel inclined to continue eating less well on weekends, at least try to eat not as many calories. As we get older, it's somewhat natural for our metabolism to slow down a little bit, so you might have to cut back on your calories. There are numerous sites on which you can find "calorie counters" that will help you figure out how many calories you should eat/drink per day.