Glutamine unfortunately seems to make symptoms worse for me. Sounds so promising for leaky gut, but I wonder if it could disrupt the balance needed to avoid glutamate toxicity.
Niacin seems okay for me, but doesn't help with the headaches or migraines much. There's a small benefit if I can manage to take it before the headache starts, but even then it's minimal. I've also tried the non-flush type, and that doesn't seem to do much. I've tried combining it with methyl donors like TMG or SAMe and so forth. Small energy benefits, but doesn't affect the acid reflux and migraines.
Heartburn can manifest as chest pain, coughing (that's one of my big ones), sour stomach, and so forth. Depends on the type of heartburn as well (LES, etc). It's very frustrating. Things that seem the best (for me) at mitigating it to some degree: slippery elm, fenugreek, marshmallow, dairy (seems like a no-no, but surprisingly I do better when eating dairy as opposed to cutting it out), not going to sleep with an empty stomach (another surprising and counter-intuitive one for me), melatonin, antacids for temporary relief (only helps for a bit and doesn't affect the proceeding headache), etc. Just got some aloe vera to trial again - wasn't helpful in the past, but it's been a few years since I tried it last.