OK, first some general notes, then I'll get to specifics of your report.
As a contractor, I have little use for home inspectors, unless they're of the "old guy who spent decades in construction and now is a home inspector because it's less physical wear & tear" type. Those guys are worth their weight in gold. But there's not nearly enough of them to keep up with the real estate boom. The other major types are:
- Failed in construction, was frustrated that his genius was never recognized, decided to go be an inspector so he could find fault with others' work. (A lotta these guys are building inspectors, too.)
- Have never worked in construction. Learned from a book or online course.
Then add on top of that, inspection standards make them afraid of getting sued, so they call out all kinds of minor crap that every single house in the world will have. I've seen them terrify buyers over nothing, because there's no perspective to their reports.
It's still better having a home inspection than not. I just wish there were, by and large, a better pool of home inspectors out there. (By the same token, people feel the same way about contractors....and they're right!) That's just background, saying "Don't freak out over inspection reports."
Now, all that said, there are some things that concern me in this report. I would ask for an extension of the option period in order to give a real contractor a chance to look at things. The items that are of particular concern to me are the structural issues:
- There is a noticeable bow/sag to interior ceiling within home AND to roof ridge. The cause was not determined.
- There is ACTIVE evidence of more than one kind of wood destroying insect found in the crawl space. The insects appear to be anobiid beetles AND carpenter ants/moisture ants.
- A licensed contractor will need to "sound"/inspect the structural members under the home to determine which, if any, should be replaced. This should include the main beams, posts, sub-flooring, and floor joists. (I'm assuming this is related to the WDI...they can screw up structural integrity. Usually, it's readily fixable, but they can in some instances do serious damage.)
- It is recommended to modify/replace stacked block support under home with one properly-sized wood post secured to concrete pier pad AND gussetted to beam support
Other stuff, like the plumbing leak, reversed polarity, WDI, discharge pipe, vapor barrier - that's all stuff that can be fixed in a few hours each. If I was the seller, I wouldn't bat an eye at being asked to repair those and complete the sale. Other stuff, like the attic ventilation, is no big deal to me - most older houses won't meet current standards. But the thing you want to avoid is big structural issues that can cost tens of thousands to fix. Get a real contractor in there and evaluate. Don't be afraid to walk away if the deal isn't right.