Has he been checked for tongue tie VP? DS had a posterior tie which can cause problems with being able to open their mouth wide enough. He also had a ventouse delivery and apparently it's common to have problems opening mouth wide enough (especially on one side as it's a bit like they have whiplash on one side).
The LC that did his tongue gave me a great link with heaps of other links, videos, etc on it. The video on 'the pumping station' link is good.
But for this particular thread/issue I googled 'latching with a small areola' and some articles popped up saying to put the whole areola in and also one that mentioned a 'bulls eye' latch rather than the now widely popular 'asymmetrical latch.'