You should be able to do that upgrade without any particular issues.
You should definitely be able to do it if you use a freshly flashed CF card.
You should use the largest image that will fit on your card. Some 4GB cards are actually smaller and won't take the 4G image. If it writes to the card without error though you should be good.
Did you try running 2.2.X without restoring your previous config for any length of time?
The biggest issue with those older ALIX boards is that they only have 256MB of RAM which is restrictive. I suspect that you have some packages loaded that are exhausting the memory. The system logs should show that though or the console output if you have the serial console hooked up.
What USB device are you using there? It's possible something in the FreeBSD 10 drivers is having an issue with it. Logs should also reveal that.
Steve