I've said this on other threads, but you can get someone to come in (I use a plumber) and camera-scope your french drain/weeping tile system (that is on the outside) and many times via the drain access on the inside. It may tell you something and may not - but for $350 it's a lot cheaper than tearing down decks and such.
Check it out; if your weeping system is blocked or non-existent, it'll tell you that. But IMO it's money well spent as it might just pinpoint a local problem that can be fixed relatively easily. At least get their opinions...
1. closed all vents
2. 6 mil plastic over the dirt floor.
3. interior drainage around the whole crawlspace.
4. all trash old vents, old insulation removed from dirt crawl.
5. deeper sump pits in dirt and concrete crawl discharging off property.
6. outside access hatch installed.
7. Still have the dehumidifier raised off ground and running.