TromboneChat

I need some information from some experienced trombone players. I am 75 years old and currently play with the musicians at my church. I currently am playing a full bore horn. I have had some health issues the past two years and I struggle to have enough wind to play like I want to. My question for you experts is, would a horn with a smaller bore make a significant difference?

Yes.
And the mouthpiece can make a big difference too.

Doug thank you so much for your reply. Do you have a suggestion on the bore size and mouthpiece to help me, The mouthpiece I am currently using is a 6BL.

I don't make blind recommendations without seeing you play. There are too many variables both on your side and the equipment side.
Skype?

One thing is you might want to get exposure to is what the other options could feel like and if it would make a positive difference or not, just to get a data point. Consider asking around at church to see if anyone (or possibly their kids/grandkids in a school program) have a horn you could borrow even just for a day, otherwise see if you could visit a music store that does rentals. (You won't find much if any mouthpiece diversity though)