Also under the support tab there is a box for "separation from part". The higher those numbers are the easier it is to separate. If you print with 0 separation layers for instance thats pretty much the same as if the supports are supposed to be part of the actual part. Could be handy for dissolvable support material though.
Do the support separations settings effect raft separation? It's true that the bed should always be perfectly level etc... however I have to say that having a raft that easily separates would be convenient. It appears that if you elevate the object (change it's abosolute z value) so that it's above the raft, you can generate support material between the raft and object. So I guess that would be a workaround.
I'm printing ABS with "ABS-Juice" on a glass plate. That works really well for me. Printing Temperature 230°C, bed temperature 110°C.
Simply put some ABS Filament parts (or remains of a print) in some acetone in an acetone proof, lockable container. Wait some hours until everything is dissolved.
Before you print simply put a thin film of ABS Juice on your cold build plate and wait until it is solid.
This doesn't work with PLA. For PLA you need Tetrahydrofuran