I have a Dreamer as well, but I haven't used buildtak sheets. I always print on glass, so not sure how much I can help, but I do have a few thoughts. Most important is that when I'm printing with ABS, I'll usually wait to remove the print until the bed cools down. Very often the print just pops loose of the bed on its own when it gets cool enough; if it's a lot of surface area I'll actually hear the "crack" from the other room.

If I'm trying to print multiple objects without stopping to cool and reheat the bed I'll use a putty knife to pop the first print off. I tend to set the knife flat on the edge of the bed, then stab at the juncture of the print and bed -- I don't want to slip it under and do too much prying because I could push the bed out of level. Sometimes a couple of jabs will break the seal between bed and print, but sometimes I do have to wait for it to cool.

Another thought -- 230 seems rather hot for ABS. Which brand and color do you find that needs to be that hot? I'm wondering if the whiteness you're seeing is actually the color being burned out?