1. 25's will be fine on a dirt road, maybe not ideal, but don't worry about it, just ride. Someday when they need to be replaced throw 28's on they'll be a little more forgiving.

2. You absolutley don't have to carry stuff to fix your bike. You can always walk in the event of a breakdown. You can carry a cell phone and have your wife come and get you overtime something happens. Or you can put a small seat pack on the bike with a tube, patch kit, co2 inflator or pump and a multitool and take care of most common breakdowns quickly and easily yourself. It's up to you.