Help needed please no power no start

Hi all, sorry for this long first post but, I am in need of getting my recently purchased 1979 Coachman class A 454 with 79,000 miles started. I am stuck in Texas at daughters house with a no start condition. Here's the low down. I drove it all the way from Illinois to Texas. It Started and ran good all the way here. Soon as I parked it and let it sit for a few days using shore power, I tried to start it to go empty the tanks and all I got was a click. Tried tapping on the starter but upon closer look at the starter, the solenoid with plastic cover was fried. I recently purchased this old heap (first RV) to have a project to work on through the winter down here and the previous owner included some new parts, one being a starter. So I replaced it and repaired the terminal ends on the little wires too. I also noticed that the main ground hub on passenger side, where ALL battery grounds are attached, (coach and chassis) was rusted. I tried to take it apart to wire brush the bolt and cable ends but it broke. I drilled a new hole and installed a new 3/8" bolt and re attached all the grounds and it then started and I ran it for 20 minutes, and took the opportunity to run the generator too. I thought all was well so I shut it off. 30 minutes later I tried starting it again and all I got was the same click again, so I re-inspected all my work and verified it was all good. I had my grandson try turning the key so I could better hear where this click noise was emanating from and it was coming from a rusty tin can with 4 terminals and wires near the alternator underneath the dog house. I read a little bit on this device and I assumed it was an ISOLATOR. I also saw one underneath the hood near the engine and (single) coach battery. They were both rusty and old looking so I ordered 2 ISOLATORS from Amazon and installed them being careful to re-attach all the wires the same way while also replacing the wire terminal connectors too.
I then tried starting it and got nothing but a click AGAIN! To make matters worse my daughter and son in law were given a warning by the city of Mesquite to move this old heap off of the grass and onto the paved driveway or else it will be towed. I have until the 19th to move this thing...
I have come to learn about the Chevy hot start problems and the Fix using a 2nd starter solenoid some even using a Ford unit. So I may have replaced the 2nd start solenoid on top of engine with an Isolator instead. I tried to bypass the thing and attach the wires together that were at one time spliced to accommodate this 2nd solenoid. BUT I forgot to disconnect the battery and sparks ensued smh..so I think I may have shorted something out that is currently preventing any power to the engine starting circuit.

What I have done and checked so far..
I checked and re-checked all the grounds I could trace pertaining to chassis starting circuit including big strap on left side of engine.
The chassis battery has been charged 2 times and currently at 12.67.
No power at the replaced Isolator can thing. Did I buy the wrong part?
I have power from battery to the big starter terminal BUT none at the small terminal that goes to ignition switch(?) with key on or off.
Disconnected ignition switch plug, no power at all key on or off.
I replaced all the fuses with new ones. No power at any of them.

I am going to remove the new starter and run cables to it to test it to see if the starter solenoid may have shorted and fried not allowing power to ignition switch?.
I want to replace the fusible links at the starter but need to know where others may be..was told that there may be one at the alternator and ignition switch?

Don't know what else to check off the top of my head..Any help from anyone regarding this is greatly appreciated. I'm stuck here with my dog, my funds are being depleted and I don't want the vultures from code enforcement taking my home to a junkyard..Any Chevy techs with experience on these old coachs please help!
I can post pics of this monstrosity if the site allows me to..