Solar System Purchase for Weekend Boondocking

Looking for some advice on our upcomming purchase of a DIY 12v Solar System. We've done lot's of research and we are on a small budget. Our frequent trips are usually 2-4 days at a time. We really only NEED to run the water pump, propane detector and a few lights. This totals 6-7 Amp Hours / Day using online usage calculators = super low usage.

Here is the 100W Solar Panel we've decided on. $169 & free shipping:

http://www.amazon.com/RENOGY-Monocrystalline-Photovoltaic-Battery-Charging/dp/B009Z6CW7O/ref=sr_1_1?ie=UTF8&qid=1387034158&sr=8-1&keywords=100w+solar+panel

The Converter in our travel trailer does not work. So rather than replacing it we are going solar. We almost never hook onto Shore Power (dedicated boondockers). So, when we install our little solar system, what will we lose by not having the converter? and will there be wiring problems created by the not-working converter/charger?

Charge Controller: We'll get the best PWM w LCD that we can afford. MPPT is just too expensive:

http://www.amazon.com/Amp-PWM-Charge-Controller-Display/dp/B00FB3OPKM/ref=sr_1_2?ie=UTF8&qid=1387034226&sr=8-2&keywords=30a+charge+controller+with+lcd

We currently have a typical cheapo 35 Amp Hour battery. Could this setup handle:
1. A second battery?
2. A second panel?
3. A real battery with 70-80 Amp Hours?

When finances allow, we would like to expand our system. So overall, would this be a worthy start? How would you expand later? Maybe different start up purchases?? Maybe sell all this and start again with a real MPPT charge controller???

We are soon to take the leap into this little PV solar system setup for $270-$300 and use last years battery. Then a new battery ... then 2 batteries ... and then... and then... EEEK!

And finally, will this small system require a FUSE and/or a KILL switch? Each time you cut and connect wire, you lose some valuable power. But what level of saftey is neccessary?

THANKS !!!