I would not recommend splicing a headlamp harness. Better to find used ones and replace them as a unit. The splice tends to corrode over time. Then, if you intend to use high-wattage bulbs, buy an aftermarket high-wattage lamp harness/relays. Well worth the $50 or less. I have used high-wattage systems (with harnesses/relays) for many years. Never had a problem. Currently have an 80 watt application in the Legend.
I am unclear about the handle problem. If you can't open the door from the inside, the mounting tab has broken and you need a new inner handle assy. If you can't open it from the outside, the handle has broken (they are sold prepainted). You should be able to open the door using one of the two usual methods. If the vehicle is a Coupe, you must be especially careful in supporting the inner door panel so that it does not break the inner door handle mounting tab to which the lock assy cable is affixed.