Increases like that are good in moderation. Maybe for your last set or two of an exercise but I wouldn't do it all the time. It's will put you out of the hypertrophy range and instead of 8 to 10 reps you might be at 4 to 6. So only do those at the end of a an exercise in my opinion
Some use it and some don't. If ypur estrogen is controlled right you likely will experience great libido and hard one and won't need it. Estrogen too high or especially too low and viagra won't even save your dick
Dylan gave you a great stack. Look at your diet as well as your training. That will have a big impact on your body and keeping it from breaking down. I'm 50. You don't need to fall apart in your 40s