1. The pump allen mounting bolts are frozen in place. I purchased a metric allen 3/8" socket but it only served to round out the allen hex inside the bolt. So, how about I use my Makita to cut the water pump off the engine in pieces to get at the bolts? (I no longer care about losing the $60 core charge)

2. An electric cable threads through the water pump to a sensor at top of flywheel damper degree wheel. What is it and what precautions to remove it. Is position critical?

3. I had my thermostatically controlled fan clutch replaced by the dealer ($400) last year but now can't get it off. I have the big allen tool but can't figure out how to hold the belt/wheel to keep it from turning when I try to loosen the bolt. I now have the radiator out so have a bit of room (don't know how anyone would do this job with radiator in place). Do I read the manual right that there is a hole somewhere in the wheel which can be used to pin the wheel in position so the bolt can be removed?

4. I do have radiator out being core/cleaned/re-rodded at the radiator rodding shop. The serpentine tensioning assembly is removed and the power-steering pump is laid back. Dealer wanted $800 to replace the water pump and now that I've got parts all over the garage and I'm working in the rain...wish I hadn't started this thing. I desparately need hand-holding.

Tell me nice things please, being 70 wasn't supposed to be like this. Criticize my need for a haircut or my spelling and I'll ...

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1993 MB190e 104k

Your situation isn't dire. I'll suggest a few things, but I'm sure other's more familiar with your model will respond.
Question: Can you get a set of vice grips on the head(s) of the allen screws? If so, that might solve your problem right there.
Comment: Take some cutting oil (oil to lubricate and remove metal shavings when cutting threads with a tap or pipe die) and squirt a little at the surface contact between pump and allen head bolt.
Comment: take a small cold chisel and lightly tap on allen screw such that the cold chisel is place so that the tappin tends to loosen the allen bolts.
Comment as far as keeping the pulley from turning, depending on how your belt circuit is configured, place a strong downward force on the belt (or pulling force if you need to pull up the bottom end of the belt. This solution is not best, I would think. Look on water pump and/or pulley to see if you can find the hole for a screw driver or drift pin so that you can lock the pulley in place. It is best, I would think, if you could get pulley off, it will be relatively easy compared to removing the water pump, per se.