It may depend also on how accurate the 22 and 48 were. Was he already 22, or almost 22, or in his 22nd year?
Same with the death - was he actually 48, or in his 48th year, or so close to turning 48 that they used it instead of 47?
Mostly, though, I'd go with what you figured -- born between 10 June and 9 September 1865.
Or use "born in 1865, seemingly between 10 June and 9 September based on his given ages at marriage and death".