Sounds to me like you have an issue with your computer. All of us use cards (I use SanDisk 64's) with no issues. If you've tried several cards with the same issues, and the issues include things exclusive of the DX50, then I would look for a computer/cable issue. The fact that you don't seem to want to use a reader also complicates things, as a reader allow you to see where in your chain issues are cropping up.
I would suggest buying a reader for less than $10 and also trying a different cable. Reboot your computer first. See if files load onto a card using your computer cleanly. If they show up perfectly on the card after loading them and then unmounting/remounting the card, you will know the card is fine.
Try rebooting your DX50. Make sure it is empty (sounds like you've been fussing with it, so clear everything out of its internal storage). You could even reinstall its firmware. Then try a card. And keep in mind you might be having problems with your files because something is going on with them, a corruption, bad tags, whatever.
I use many Apple products and find that the iBasso is no better/worse in terms of ease of use. It has less ease-of-use consumer features than an iPod, but the quality is certainly far superior and I've found that the DX50 UI is certainly easy to use.
People here are giving you good advice. Try some of it. It may help.