Should be easy to splice the wire. Ideal would be strip a bit of insulation, slide some heat shrink tube over the wire, twist the exposed wires together, solder, then slide the heat shrink tube to cover the soldered wire and heat it. But you can probably get away skipping the soldering.

The need for breakaway fender struts is less if you have plenty of clearance between tire and fender, and less if the fenders are steel and "shortys" like yours. I wouldn't worry about it, but I also would try to avoid riding through piles of debris, over branches, etc. That is a general safety precaution for all bikes.