First, yea - I agree totally with the advice to ditch the wide angle. Now if you can afford it, get it now, but if it's a financial toss-up, go with one strobe.
I bought a wide-angle lens for an earlier outfit (Canon A570 in Ikelite housing) and have used it about... twice. We just don't get enough days where I really need a wide angle shot here, but then I am a 'critter photographer' and swimming rock fish are just as good on macro.
If it's a wet lens, you can put it on underwater (I did) or else get the camera & lens wet before you splash and install it. Sometimes underwater you have to remove & replace it to get a bubble of air out. You want 100% water between a wet lens and the housing glass.
As for the strobe, TTL is as simple as a) buying a strobe that supports TTL. The Inon S2000 (and the Z330) support TTL 'out of the box'. The TG6 supports TTL, so enabling TTL with the Oly TG6 is as simple as turning on the flash on the camera (there's even a quick button for that). You do need an optical sync cord connected between camera and strobe. On my TG6 with Inon S2000, I use 'fill in flash' as it gives me the desired effect, although 'full auto' does also work.
Backscatter actually has an awesome set of videos all about setting up a TG6 for underwater shooting, as well as video on setting up the strobe.
As always, take test shots out of the water to ensure it's all working before you get wet. Nothing worse that messing up the setup (lens cap inside a port anyone) and finding out underwater.
Hmm, I'll probably grab both then.
Do you leave the video light on when you go to actually take the shot?