Not bad for someone starting out! I think going for the wide angle lens vs. a second strobe was a good decision based on your preference for wider scenes. I think you'll find that with a compact like the TG-4, a single strobe is sufficiently powerful to light your foreground subjects IF you are sufficiently close to them. So.. obey the number one rule of underwater photography -- get close, and then get closer! No strobe is going to be effective if your subject is more than a meter or so away. Getting close to your subject will also help reduce backscatter. If you're consistently getting 30cm or so away from your subject and still seeing unacceptable levels of backscatter, it may be that the conditions are simply not condusive to wide-angle photography. I've found that good visibility is a key ingredient to shooting wide-angle underwater. If there's too many particles in the water, you're better off switching to macro photography or researching more advanced lighting techniques like snooting. The books I recommend below address this in much greater detail.
I think some tuition time, and especially time in the water with a good underwater photographer who can mentor you would be a valuable step in improving your photography further. There are many great educators out there--many of them active in these forums--who offer seminars and photographic workshops, often in locations full of great photographic opportunities and with other divers of the same mindset.
Another resource that has helped me tremendously in improving my underwater photography technique and may help you as well are in-depth books on the subject. Three I can recommend in particular:
The Underwater Photographer, by Martin Edge
Underwater Photography Masterclass, by Alex Mustard, and
Underwater Photography, by Tobias Friedrick
For the cost of a few dives, I think those three books are a no-brainer to any aspiring underwater photographer's development.
For wide-angle photography in particular, you'll find that balancing the ambient light (or background) exposure with the strobe light (foreground exposure) is very important in creating pleasing, color-rich images. You can start my trying to shoot with your strobe in manual mode rather than TTL to control the amount of flash exposure for the foreground. Controlling the ambient light exposure will be a little tricky with the TG-4 since you do not have full manual controls over the exposure, but you can try using the exposure compensation feature. Try underexposing by 1 stop or so to let in less ambient light, while setting the manual power on the strobe high enough to bring color to your foreground subjects without overexposing it. The beauty of digital photography is that you can take a shot, review it, and adjust your settings as necessary then take another shot -- this shoot, review, adjust, shoot again workflow is a great way to improve.
Good luck, and keep shooting!