Thanks "JZZ30" and "Deton8ed" for all the help. The solenoid contacts ended up being the problem as you both predicted. I bought new starter solenoid contact kits for the battery terminal and the motor terminal from my local Toyota dealer and saved about $20. I bought some car ramps, a 3/8" drive universal-joint socket adapter and a 20" - 3/8" drive extension and was able to repair the starter in about 4 hours 15 min. The starter was a bear to get out of the car from the bottom, but after playing with it about 15 minutes, I was able to squeeze it out the bottom through a very tight space. Once it was out, I opened up the solenoid cover and discovered the worn solenoid contacts. I cleaned the inside, polished the solenoid brass piston surface, and installed the new contact kits. (NOTE: for re-assembly, the factory manual instructs you to hold down the solenoid contacts with a piece of wood using about 200+ pounds of force while tightening the contact nuts. This was WAY too complicated. Instead, I just held down the solenoid piston against the contacts as hard as I could by hand, while tighening down the two contact nuts. For final fine-tuning adjustments, I cut a small piece of paper and held it down between the piston and each end of both solenoid contacts. If the paper slipped out of one end of the contact, I used a wrench to slightly rotate the contact to make sure that the paper was snug. After doing this on both contacts, I was assured that the total contact surface of both contacts was level against the solenoid.
Finally, to make sure that I did not twist the battery-side terminal contact when re-attaching the battery wire, I tightened that nut without the wrench - I just attached a socket to a 12" extension, and tightened the nut by hand (no wrench).
After re-assembly, the starter fired up like new (as predicted by both of you)!!!