@kahkej What percentage of saline do you nebulize? When were you diagnosed? Regarding burning in chest sounds like some variation of GERD. Trying a H2 blocker (Famotidine, aka Pepcid, Zantac 360) might help. Also stopping all food and drink 3 hours before sleep helps as does sleeping at an upright angle, for instance, on a wedge. Certain foods can trigger GERD and burning in chest. For me it's onions, a lot of garlic, and dark chocolate if I overdo.

This page describes symptoms of an exacerbation.
https://www.bronchiectasisandntminitiative.org/Learn-More/I-am-a-Patient-or-Caregiver/Exacerbations