Mercedes multiple electrical woes

Hi, I recently paid someone to modify my 1978 300D with an electric heated Davco fuel filter/water separator to use SVO. He also installed an additional electric fuel pump. I live in Oakland, but the work was done while I was in LA. This is not my daily driver, but I would like it to be. Unfortunately, I haven't done much nighttime driving and only recently noticed some odd behaviour with the indicator lights. Most everything else seems to work, but I am not an electrician and was hoping someone could help me out here.

Of note, everything seemed functional after I purchased the car, before getting the modifications done. I don't want to blame the mechanic I used, but it feels fishy :-( 1) Instrument Cluster: one of the bulbs is simply missing - the Brights Indicator. More annoyingly, the Charge Indicator, Brake Pad Warning and Parking Brake lights all stay on dimly after ignition. As the rpm's increase, the lights fade out. I am pretty sure it is a bad ground as the alternator is outputting sufficient charge, I've replaced the voltage regulator (to no effect), the battery is under 2 years and the belts are all tight (recently replaced prior to my purchase). The Turn Signals, Glowplug Indicator, Fasten Seat Belt lights, Clock, Temp and Tank guages work properly. Not sure about the Fuel Reserve Warning light, haven't let the tank get that low yet. 2) Panel lights for the dash and climate control no longer are on. 3) Headlight Warning Buzzer - doesn't come on anymore when the lights are left on and the door is opened. Those are the items which used to work.

These ones were as is when I bought the thing. 4) Rear Window Defog - only two of the metal wires seem to conduct and melt away the frost. 5) A/C wasn't working when I bought it. It'd be great to find someone who is failiar with the particularities of the Climate Control system as well. I am sure the A/C is expensive to fix, but the climate control heating seems to work intermittently. 6) Most annoyingly the fuse box seems to have been bypassed or otherwise modified from the stock set up? I am no electrician and may simply misunderstand the circuitry. I do have a simple multimeter and was just testing each fuse circuit and if I am reading things correctly, there wasn't power going to each fuse? Do the components on the circuit have to be turned on for power to get to the fuse panel? Any help or advice on how to troubleshoot the instrument cluster would be greatly appreciated. Thanks, -Patrick Kennedy