@cindy007 MAC/NTM specialists will recommend airway clearance. You mention your husband has not had nebulizer treatments, which are essential prior to airway clearance. That makes me wonder if your specialist is up to date on current therapies. Your husband has bronchiectasis and MAC. The bronchiectasis came first, then the MAC. The gold standard treatment for bronchiectasis is airway clearance and it can help MAC too. The drugs/pills alone with not cure/help MAC.

Here is a cut and paste from another post about what you need to know about airway clearance. Likely mucus is clogging your husband's lungs making him breathless. Once he gets the phlegm up and out I hope he will be less breathless. Airway clearance needs to become a habit, 2x daily minimum. No holidays or days off.

To maximize airway clearance he'll need a compressor, nebulizer and hypertonic saline. All are available without a prescription. Below are links to nebulizer and compressor, both of which have been recommended by National Jewish Health, one of the top respiratory hospitals in the US. Hypertonic saline (3% or 7%) can be purchased on Amazon.
https://www.saveritemedical.com/products/ombra-120v-table-top-nebulizer-compressor-system
https://www.amazon.com/dp/B0BNNV3JW6?ref=ppx_yo2ov_dt_b_fed_asin_title
Airway clearance info
https://bronchiectasis.com.au/physiotherapy
I hope this is somewhat helpful.