Oh yes, ramadan falls in September this year. It will be quite inconvenient to get food, etc. because Aceh is a muslim state, though not as strict as KSA, they are still pretty strict. Restaurants and coffee shops will very likely be close.
Ton and Marjan are extremely friendly and accommodating throughout my stay there. Planning a trip there is easy with all the information they provide.
I haven't been to Redang, but I've been to many nearby islands around that region. I've been to Perhentian Island, which is very close to Redang, with comparable diving. Diving there is good towards the end of the diving season (Mar-Nov). Sept and Oct would be one the better choice in terms of visibility and weather.
Hey, I'm considering Komodo in Dec during xmas too!!!