My Gates housing has mounting holes in the handles for lights. I use Ultralight arms, some people prefer Locline and others TLC arms. Not familiar with your housing so I can't really offer any suggestions other than to ask the mfr if they have some kind of tray or mounting plate that goes on the dovetail.
I currently use 2 lamps, but started with a single. The beam is wide enough for macro. 1 lamp is good, 2 is better. If I were just starting with a limited budget, I go for 1 lamp and get the 2nd later on.
The cannister comes with a loop for mounting on a belt. I believe Sartek also has stainless steel hardware options for mounting on a tank or clipping onto BCD "D" rings. I prefer to simply wear it on my belt, cheap and easy. If you go with the setup I have, you will need to buy the canister with the wet connect option since the Sartek halogen test-tube lamp is a wet connect. It's a great option because as you stated, I enter the water wearing the canister and then have my camcorder handed down to me. While in the water I wet connect the lamp to the canister.