I agree with Alan. What's wrong with your current
should be running off 12V - so you don't need the inverter for those.
If it's the charger
that's a problem, you can get a really nice separate one for a lot less than a new inverter/charger.
Also, most Sharp microwaves will run fine, but they put out less power off a non-sine wave inverter. A full sine wave inverter will run pretty much anybodies.
power supplies don't like modified sine wave inverter power, but you should be running your laptop
off a 12V power supply anyway!
Your poor Terminal/Cable connections - are they just dirty or loose? If so, they're easy to clean.
$75/Hr. is at the low end of the range for a good electrical
guy in the PNW.
Good luck with your fixes.