Root HTC Evo V 64GB Micro SD, Weird problems

So i ordered a 64gb Micro SDHC card off of eBay after hearing that for the most part these cards are compatible with my phone (HTC Evo V) and often require little trouble to get them to work. The card shows up just fine in the phone, under settings it shows that something like 62.5gb are available on it, but the weird thing is it will only use about 3.7gb. I got a 64gb card to hold all of my music (~34GB) but when i transfer it the weirdest thing happens: when i transfer the files over directly to the cards "Music" folder the files only transfer at an average of 2.5mbps, and after waiting hours upon hours for everything to transfer everything shows up in the music folder (looking at the sd card's folders through Windows). However, when i unplug my phone and look at it only the first 3.7gb of my library transferred over. In the settings-storage tab in my phone it always shows that music takes up 3.7gb, as well as Temporary files taking up a similar amount. Then when i plug my phone back in all the songs that were in the music folder have somehow disappeared other than that 3.7gb.

I downloaded and use doubletwist as a suggestion from others, but still the same thing happens. Ill plug in my phone and sync it to my library: the phone will load all my music in a few hours, i can check the folder through Windows and see all my music is there but when i unplug it most of it disappears and only 3.7gb is left.

I've tried refformatting the card (it is currently formatted to FAT32) and nothing has seemed to help. I;ve searched far and wide across the internet and I have not seen a single sign of a problem like this. Any help is greatly appreciated!!!