Bulldogs World

My male bullie, Clem Bob has always been pretty healthy. This dog barely snores and has never had breathing issues. We have always had an elevated bowl and bought good dry food.  He used to be overweight and we switched to diet food and then food for older dogs, but over time and not recently.  The food we were using was about dime size, maybe slightly smaller, one cup a day in the morning.  This has been the same since we got him.  No problems until like the last couple months.  He just started throwing up what appeared to be his whole meal with lots of thick saliva.  Twice he was choking, and fortunately my wife (a nurse) was with him and had to basically use the Heimlich to save him.  Had she not been there, she said he would definitely not be with us.  He had fallen over and started convusling.  

We have switched to a much smaller food size, and 2-3 small meals a day.  He is surviving, but seems to still be generating lots of thick saliva and seems to try to clear his throat fairly regularly (sounds like he's trying to bring up major flem).  Besides sounding completely revolting, there has to be something better. 

I see suggestion for probiotics, but for an older dog? I know he's unusually old, but there must e something we can do for him.  Water in his food?  Wet food mixed in?  Any suggestions?

Thanks.