It seems very unlikely to me that overuse of the suction machine is causing your husband's stomach problems. Lack of saliva causes many many problems, but as far as I know, not stomach issues or vomiting. Almost every OCF patient has struggled with lack of saliva and the resultant Xerostomia (medspeak for dry mouth). It's "normal". Actually, too much saliva can cause stomach problems, including reflux. but not too little. The canned nutrition is formulated to be digested in the stomach and does not need any saliva predigestion.
I used my suction machine all during the day and got up several times during the night to use it. Actually it helped prevent vomiting since when the mucous would get stuck in my throat, it would trigger a gag reflex.
You do have a serious problem with his lack of nutrition.
Here is a recent thread on someone's similar (not exactly the same, but we are all different) problem. Unable to keep food down thread
One other possibility would be that he needs a pump to slow down his feed. Christine B is our resident expert from personal experience on those issues.
I'm sorry I don't have the solution but I did want to reassure you that it's not the suction machine. He needs it. You have more than enough to worry about as it is, plus focusing on the suction machine will keep you both from finding out what is the real problem and fixing it.
Charm