Toyota Repair: starter issues...?, connecting jumper cables, advanced auto parts

Question
I have a 1990 toy 4-runner,4x4,v-6,AT. When purchased (used) July,2011 mech. at dealer said "I may need to replace starter soon,due to clicking sound and that I may have to tap starter on side with somthing (via.- inner r> fender well)"if it didnt want to start. 'bout a week later,sure'nuff ,didnt want to start,just a single click w/ turn of ignition. Upon looking at starter, noticed that cylinoid wire was stripped of insulation,possibly where someone had tried to create a point to cross jump with screwdriver closer to starter terminal...maybe?. I taped wire up and jumped truck w/ cables it started instantly ;but later on when this happened and had no one to jump vehicle ,I had to untape wire and cross jump w/ screwdriver. This problem  went on for about 2-3 mnths. then quit and started fine  for about 6-7 months, then problem started all over again, except now when I've tried to cross-jump with screwdriver it sounds as if starter is dragging and then goes into a  continuous clicking sound like a dead battery;but when connecting jumper cables to it, it starts immediately-no charging needed ; So I pop battery caps and noticed one cell was a little low, I added a little purified water and took it to advanced auto parts and they checked batt./alt. under load, revved up,and during start-up. everything came back text-book!! Technician said water may have helped;but to clean/check wire/cable connections. I cleaned and replaced terminals on cables to battery  and applied a little grease to them, everything worked great for about 4 days then started all over. except continually gets worse about starting and is more frequent now. I called auto-parts store and manager suggested that brushes in starter could be worn to the point of grounding out battery and slowly draining voltage ;so I check cables ,sure enough,with everything turned off ,when re-connecting ground terminal to bat,you can see and hear a little spark at terminal (as if there's a a low/steady pull  of current like a radio or int. light or something ( I know this to work on older domestic cars anyway ;but I also know alot of newer vehicles will spark due to computers or alarms (which it has a deterrent on it);so this doesnt really tell me much. It just takes spells and I've noticed the time of day and the temperature has nothing to do with it. You can even drive 50 miles, shut it off and sometimes it starts, and sometimes you have to just bump the key over and over anywhere from 2or3 times to maybe 30 times and it will  either crank right up or sometimes sound like its dragging and the batteries dead ;so I figured I'd look online to see the best way to remove starter to get it benched tested and after reading alot of other post by people w/ the same issues,I;ve noticed alot of talk about starter relays, cylenoid terminals wearing uneven which in return causes a voltage drop at starter (which sounds like my scenario-due to the fact that the use of jumper cables seem to help it start real quick( What I mean here is that: you don't have to let it charge to crank and it doesn't spin over and over to start.It cranks  instantly and you can immediatley shut it off and it will crank right up without cables) I've also read a few post that have said the cylenoid wire is only a 20 awg. and will not carry enough current to crank as it gets older and breaks down;but my wire looks to be at least a 14 or even 12 awg.      ...;So I thought I may get your opinion as to what theory may/may not apply to my issue without me haveing to replace an UN-needed starter ,seeing as to how its bad enough to even get to it once to work on and I'm partially disabled and unemployed ;so i have to do it myself and cant afford to buy a starter if its not needed and dont physically feel like doing it period.. bUT ALSO DONT FEEL LIKE GOIN THRU THIS ANYMORE!!! ;so your advice would be greatly appreciated and thanks again  God-bless!!!

Answer
Hello, if you can hear the starter clicking then the circuit to the solenoid completes, this usually means the starter has to be replaced, the reason it may start by jumping is that there is more current available due to the two batteries connected in parallel.