While you have a breaker for your water heater, it only controls the 120v element and not the 12v/LPG segment. You should also have an automotive style fuse in the bank of them (next to the 120v circuit breakers) that will disconnect the 12v. You really don't need to kill the circuit breakers though...leaving the individual devices off will remove them from drawing current since the 120v appliances (television and A/C) won't run on 12v, so, unless you are plugged into shore power, there is no current for them to draw. The biggest 12v drain is going to be the lighting, the Jensen radio/CD/DVD unit and your LP gas leak detector and the LP Detector, for safety reasons, has no provision, short of cutting the power wire, for turning it off and depending on your model of trailer, the Jensen may or may not have a fuse in the fuse panel... In some models, the Jensen fuse is part of the wiring harness; you would have to pull the whole unit out of the cabinet to get to it. 12v lighting is also a huge power draw, that's why many folks that spend most of their time off the grid convert to LED lighting; ample light at a fraction of the current draw.
The clicking is the DSI unit igniting the small pilot flame for the refrigerator. In all my years of RVing, I've never heard the burner for a refrigerator...the DSI clicks, yes, the burner, no. It is just a small pilot flame and should not be drawing so much gas that it whooshes. Normally, once the unit fires up the first time, it ceases the DSI multiple clicks. The multiple clicks happen because the LP bleeds out of the line over time and it can take a minute or so to refill the line from the tank to the device (whether it be your stove, oven, water heater or refrigerator), but, once the line is full and is in use daily, it usually doesn't bleed off that fast as long as you leave your tanks on. Once the line is filled, one click and it should be lit unless you have a constant 30 mph gale blowing directly at the outside refrigerator access/vent panel. If you are turning your LP tanks off, that is why you get the multiple clicks, or you may have a leak that is letting the gas in the line bleed off. As for the water heater...it doesn't use much electricity (12v) in LP mode. We do not leave our water heater on all the time. We turn it on for about 15 minutes at night...it heats up that fast on LP and then we turn it off. Plenty of hot water (6 gallons) for washing the dishes and a quick wash up before bed. If we take a shower, we leave it on just for the duration of the shower (short navy showers) if we are off the grid. Again, the refrigerator and the water heater (in LP mode) don't use very much current (12v).
As for blowing the fuse at the battery... How is your battery hooked up? Many folks, new to RVing, will hook the battery up with the white being hot thinking that the black must be ground. In an RV, that is backwards. Black should go to the + post and white to the - post. That's the only reason I can think of that would cause the fuse at the battery to blow when you hooked up your shore power...the convertor tried to push ~13.5 volts of positive DC current down the wire into the negative terminal of the battery in the attempt to recharge the battery. If that is the case, you may have also damaged the convertor. It would help to know how you hooked up your 30 amp power cord to your diesel generator...does the generator have an RV 30 amp socket or did you use an RV 30 amp to 120v plug adapter? If your trailer is older, it is even possible, assuming the battery cables are hooked up correctly, that you may have a defective convertor. If the convertor tries passing too much charging current to the battery, that will also blow the fuse at the battery's cable...
My 2 cents, your mileage may vary...
2 Cats; J-Lo and Ragamuffin :R
2014 Thor Tuscany 40RX DP
2011 Ram 2500 Longhorn CTD HO
2011 Keystone Cougar 318SAB (now gone)
2008 FunFinder X 210WBS (Sadly gone)