You may be able to run a bead of silicone around the bulkhead from the outside of the tank without taking the bulkhead off. Make sure it is dry first. It will make it harder to remove later but not impossible. Best thing is to remove the bulkhead, clean the glass around the hole, clean the gasket and the bulkhead then put it all in. A thin film of lube or silicon on the gasket may help it seal but if everything is clean and smooth the rubber gasket should do the trick by itself. Just make sure it doesn't buckle or get pinched while tightening it up. You don't want to tighten it too much like you said but I don't know that "Hand Tight" would be enough. Get it hand tight then, with a wrench, carefully tighten it another 1/4 turn.
Since my tank is a birthday present to my wife, everything I spend going forward is just an extension of my love for her right?