Hi Puddleduck
My first tip is to book in to see the orangutans as soon as you arrive at Rasa Ria, because they only allow a limited amount of visitors for each session and once you've been, you'll probably want to go again before you leave! Your itinerary makes me feel exhausted just reading it, so I hate to add any more ideas, but if you aren't already doing one and get chance, do consider a river boat trip. We've done two in Borneo - the first in the Klias wetalnds near KK and the second on the Menanggol River near Sandakan and both were major highlights of our holidays. The amount and variety of wildlife along the rivers is amazing - especially if you have a good guide to point it all out to you.
As for the mozzies, my best tip is don't be tempted to wear shorts or short sleeved T-shirts in the jungle, even if it is steaming! I wore long, loose linen pants and a very thin, but long-sleeved shirt, which both looked extremely disreputable after a couple of days, but the wildlife didn't seem to mind and I was glad I had when I saw other people's arms and legs covered in bites.
We had a brilliant time on our trip this April and Langkawi was a very welcome veg-out after our adventures!
Elaine