Crawlspace perimeter drain and sump pump needed?
Is it water vapor or water that you are dealing with?
If it is water vapor, then the footing drain will not be the solution. If it is water vapor, condensation may be forming on the bottom surface of the vapor barrier. It would do this if the vapor barrier was at the dew point temperature. If this is the problem, try keeping your vapor barrier at a temperature above the dew point temperature. (Perhaps by insulating on top of your vapor barrier, etc.)
If it is subterranean water, the drain will help. You could dig a few 6 inch diameter holes in the floor of the crawlspace, a foot deep or so, and see if they fill up with water in a day or two. If so, you probably need a footing drain.
Regarding the dehumidifer: What is the relative humidity in the crawlspace? (Perhaps you own one of those inexpensive humidity measuring tools like one you can get at Grainger, etc.) The dehumidifer will not remove moisture from below the vapor barrier.
I had an interesting basement seepage problem years ago. My new house needed to have a perimeter under-floor footing drain retro-fitted after we had moved in due to seepage. Years later, when the next row of new houses were built, they discovered the presence of an old farmers field drain tile that had been cut during the construction of the new house. They blocked that drain tile,and it eliminated the seepage to my house.