Yep, I do agree that you first need to get that T up in the late teens/early 20ish range to feel your best.
Frankly speaking, TT is all I ever needed to work with. Never bothered with bioavailable T under “most” circumstances. I see many, many Men here and elsewhere with undue worries about FT, Bioavailable T, Pregnenolone, Progesterone et Al. These could all be pivotal markers in “isolated” cases that warrant testing, however.
From my personal experience: LH, TT, E2, AM Cortisol, DHEA-S, TSH, FT4, FT3, Body Temp, Prolactin, Liver, Kidneys, Vit.D, Ferritin, & CBC can be used to draw many conclusions and setup way-forward. Excuse my lengthy intro.
Back to your query, hard to say if popping joints is caused by low T. That said, E2 is suspect zero in my book. As I said, your current level is in a good range for “most” men given that other markers mentioned above are optimal, but try and raise your TT to drive up your E2.
I’m very optimistic this would resolve your issue.