Hmmm. I'm not a wound expert by any means, but I found a really good article that addresses the maceration issue:
The article does mention that there is no evidence that suggests that a moist dressing necessarily contributes to maceration. Another important thing to consider is if the wound is clean or infected; if infection is present, there are several products, such as alginate and silvasorb, that can be used.
You also mention that other nurses prefer to leave wounds open to air. I would NEVER choose to do that on a stage III; when a decub gets to that point, there is serious risk for infection and it can easily spread outside the wound.
It's SO challenging to get a sacral dressing to stay put once you put it on; like you mention, they really do like to wrinkle no matter how careful you are...it's just the way things "shape up" down there. On top of that there are body fluid issues to contend with if your patient is incontinent. Have you tried cutting your tegaderm to fit the shape of your individual "bootie?" Some nurses will cut a semi-circle to fit over where the cheeks separate and that often helps keep the dressing clean and intact.
I have also discovered that skin prep and Hypafix tape are my best friends as far as getting dressings to stay better. Apply skin prep in about a 2 inch radius outward from where your dressing edges will be; allow to dry so that it's slightly tacky, and apply your dressing. I'm not sure if you've seen Hypafix or Mefix tape, but it's kind of this stretchy tape that sticks amazingly to skin but peels off very nicely when it's time to change your dressing. Those two things will help your dressing stay put by 100%.
I'm happy to see your interest in wound care; as an LPN I've worked in many a nursing home and treated many a stage III/IV, and I cannot stress enough the importance of early intervention. Thanks, AmyAnn!