How do I fix this 30 ft (9 m) dryer vent abomination?
Move It!
As already noted by some others, moving the dryer to the wall where the vent ends is a great idea. The location for a gas dryer needs three things:

Vent - Absolutely perfect. While you're at it, since it will be a short distance, splurge on some rigid metal ductwork. For a short length it doesn't cost much, and it is much less vulnerable than the flexible stuff to (a) lint buildup and (b) punctures. Punctures are an annoyance with an electric dryer - the worst that happens is some hot, moist air in the room. But with a gas dryer they can be downright dangerous if carbon monoxide leaks into the room.

Electricity - You may or may not be able to turn that old NEMA 10-30 into a functional 120V receptacle, but right next to it is what appears to be a standard duplex GFCI receptacle.

Gas - You're in luck here too. Your water heater is in the closet.


Put the $ 300 - $ 500 toward a qualified plumber/gasfitter and you're all set. It actually shouldn't cost very much - basically splitting off the connection a short distance to provide a connection outside the closet for the dryer.