Electrical troubleshooting

All connections are good, there must be a part between the battery, the fuseblock and the system that is failing. Could the under-hood fuse block itself need to be replaced? You see, when load is applied, all power is lost to lights, ignition, internal fuseblocks etc, not just the starter. That is why I suspected a dead cell, but it checked out good at Pep Boys and a jump from a very good truck did no good either. Thourough cleaning of all terminals, posts, cable ends etc. Also had no effect. It slowly, as you walk away scratching your head, builds up the electrical system again for another 'click'/dead session when you return later to retry (again, dead cell symptom but not so). Lights should never stop working unless the battery is dead, or the relay is bad and the relay is good, the battery is good; I am really stumped. This is not an 'easy fix' so please give it a little more professional thought. Thank you! Waiting patiently.

I cant believe you charged me five dollars to tell me what I already know. I wanted your professional knowledge to zero in on the exact part for me to replace, otherwise, I don't need you. My message clearly stated that and you should have told me that you are not knowledgeable enough to truly troubleshoot the problem any better than me. That is something I could do and make money off of people too, but, I would look in the manuals and really research the individual possibilities for the customers to narrow down their search. I will go buy the manual now, and solve it myself, but I wanted to make sure you knew how useless you really are, and that your service is only for 'stupid' people.