Horn does not work, the seat belt is broken, and the headlights are dim.
It seems you have three issues. Any issue with a seat belt will require it to be replaced (e.g., frayed webbing, inability to retract or buckle, etc.) It’s too risky to attempt repairs with something that important. The broken horn is a pretty easy item to diagnose; the issue is usually with the horn itself, but it very well could be the switch, fuse, or wiring that is faulty.
Headlights that are dim could be caused by a few things: Check the clarity of the plastic lens; if it is foggy, it needs buffed or replaced. Headlight bulbs will get dimmer as they age; always replace them in pairs. The charging system will need checked for proper voltage. If the cause is none of the above, then the wiring and connectors will need to be inspected.
I suggest having a mobile mechanic, such as one from YourMechanic, come out to the location of your Sedona to inspect your faulty seat belt, replace or repair your broken horn, and diagnose the cause of your dim headlights.