unfortuneately I'm not in the Island at present tho' maybe SKS could check for you at Manx Museum, but you could borrow the film (see manxnotebook under genealogy for film number) of the official transcript of parish reg - it's almost certain this would confirm his regiment however I doubt if it would mention his parents, it may mention hers if she was under age - have you looked up UK national archives to see what military records survive, tho those I've seen don't give this info but might give his age. The baptismal record would not mention his family.

If you do decide to follow Margt it might be worth looking at Margt d/o Joseph Shimmin + Eleanor Harrison as Joseph died a few years after marriage + possibly eleanor remarried - but this is merely intuition on my part.