DON'T install any fans in or around the crawlspace to vent out the moist air! What you may end up doing is making the problem worst. You see, if you draw in warm, moist air into a crawlspace, where it's cool, the warm air will cool and condense making your problem worst.
As a general rule of thumb, I say install 1 12" x 9" vent per every 300 sq. ft. of crawlspace. (That's assuming a 3' height in the space.) If the floor of the crawlspace is dirt, cover it with 6 mil poly plastic, and 'hold' the edges down with some rocks. This will help keep the 'under side' moisture from rising up as quickly as it does uncovered.
I understand you took care of a rain water problem but you may want to revisit it. If you haven't already done so, the next time it rains, put on your boots and get an umbrella and inspect your gutters and downspouts. Hopefully, you get either a heavy rain or a steady one which is enough to see what's happening with the water. Your gutters shouldn't leak or overflow. They should be free and clear of any debris. The same goes for the downspouts. (If you have any underground downspouts, it/they can be leaking.) The water should be 'channeled' away from the foundation by a distance of AT LEAST 3'. The slope of the landscape all around the house should be a POSITIVE one. In other words, water shouldn't run BACK TOWARDS the foundation when it comes out the gutters. And assuming your gutters and downspouts and landscape are 'good', make sure the water has a 'place' to go. If you have a depression anywhere where water can collect, it may 'work its way' towards the foundation. In this case, you'll need to move it somewhere else where it won't do any 'harm'.
Believe me, the vast majority of 'water in the crawlspace' (or basement) problems are due to bad gutters and/or downspouts and/or landscaping. So take the time to see how it all 'works' in the next rainstorm. (Just watch out for lightening, will ya?) As for the water from the sump pump, where does IT end up once it leaves the pit? (DOes it run back to the foundation??!) Just don't add any fans. Consider a dehumidifier in the short term. DO understand that the 'pan' will fill rather quickly. (Maybe you can have it drain to the sump pump.)