1. Yes, you need some kind of protection (breaker or fuse) for the AP system.
2. Do NOT wire directly to the battery.
3. Somewhat better to connect to the house battery shut-off switch (on the house side, not the battery side), preferably to an attached house bus bar. This way you can easily disconnect ALL loads from the battery. Note that the house switch is NOT protection for the AP circuit.
4. Better ways to connect certainly exist, but depends on your electrical system
Also: depends a bit on whether this is a short term fix or a permanent installation
. If the latter, don't short cut the install. If the former, fix it as soon as you can.