Hi Charly,
Looks like you've already been to some great places
I lived in the islands for several years, and visited most of them. LIAT did a month rover ticket where you could go to any of their destinations, unlimited flights, for a very reasonable rate. Not sure if it is still available...
My personal favourite for diving is Dominica, and singledivers has a trip there soon. It is a bit different from most of the other islands, because of the volcanic activity. There is one dive site where bubbles are coming up from the sea bed. Also some amazing hiking, and hot waterfalls (not only at Trafalgar Falls where most of the tourists go) I could go on and on... I'm not going on that one because I hope to go for WCMF Dominica at the end of October. For me Tobago was better than the others, although the wall off St Croix is pretty impressive. I've never made it to the ABC islands, but I heard Bonaire is amazing.
How do you like living in Trinidad? Do you get to Tobago much? Is Dive Tobago still in operation at Pigeon Point? That was the first place I ever went diving in my life, before I was even certified. I fell in love with the islands, and it changed the whole course of my life! I still miss it so much, although I do enjoy having power all the time,lol! I've taken many baths in a bucket from the cistern when the power is out
Good luck in your travels!