GMC '02 no int. lights, etc.

I had replaced my battery and it just sits there because I need to redo the brake lines. This is an ongoing project. The battery was dying but it was 7yrs. old and was replaced. the new battery started the GMC on the spot. However, over time the battery drains. I recharged the battery in order to restart, great for that time. It drained again but now I have access to "battery pack jump started" and it works on other vehicles. I placed it on the GMC and it would only get the "clicking noise" instead of a good crank. I tried several times but finally it seems to caused a problem, no int. lights, no headlamps(dark), no radio, no ignition, though I can see the gauges moving when key is applied. None of the familiar noises when inserting key. I have checked the relay,s OK. Googled and offered possible 125A fuse maybe blown, I checked and found no fuse where its supposed to be. I get other info about RAP and BMC, but heck all this was working before the jump, and it seems a bad jump can cause the results. Is there another location for the 125A fuse? It's suppose to be next to under-the-hood fuse block, under shield.

I understand what the RAP and BCM are suppose to be doing. But more than once I found the int. fan running and thus draining the battery. I removed the small fuse to stop that. I returned it when new battery was in. Its suppose to to cut out and in general save the battery from draining. Seems to work in reverse. I can't find the 125A fuse, drains battery and now won't crank, as explained above. Is there something else I need to check. I just can't figure why the BCM would be at fault or if it too is blown.

TIA -----Willy