FYI, this forum doesn't seem to have much activity, so i would suggest looking at some other forums.
I'm in the same boat. I'm 29 , 5'-10 and the most i have ever weighed is maybe 120. I usually hover aroud 115.
I would suggest you tackle candida first, because it is the most destructive and impairs so many functions of the body - including digestion, which is the most important. Once proper digestion goes, everything slowly starts to fail...
Definitely do betaine HCL. I just started myself yesterday and i feel incredible. So energetic, great mood and feeling so grounded, like my body is like "yes! I'm getting nourishment!.