I think the only professional needed here is a psychiatrist. Whatever the issue is, between the obsession over drainage, this wall, the rat poop, and messy cabinets, a 30 year old tract house is never going to look or be built perfectly, unless you do serious work to it. Either this house gets properly and thoroughly remodeled, or it continues as just a typical moderate quality spec build from the 80's. The market in OC supports nice homes at high price points. The OP insisted on getting a cheap house or a house "at a deal." There isn't anything precious about this house, nothing historic, design forward or inherently valuable other than its dirt. I vote you either just patch it up and forget about the moisture and assume you're right about the sprinkler, or remodel the whole home, get rid of the carpet and the generic tile, put in nicely finished smooth drywall, rip out the old vinyl windows and replace with a nice clad window, redo the stucco with a nice smooth dryvit, put in nice cabinetry and fixtures in the kitchen, modernize the stairs, upgrade all the doors and hardware, redo the landscaping, put in a metal roof, put in a modern heat pump, do some nice decorative concrete work, etc...
You either really do it, or you just get it done. I see a point to a $500K renovation, or a $500 fix, but the OP continuing to get him, his kids and his wife sick from the psychosomatics of anxiety just isn't worth it.