I have beaten all 3 DKC games using SnemulDS with or without a memory expansion. So I can attest that they are 100% fully playable. And they should not freeze up at all if you use the latest version on Archeid's site.
Played on-
Supercard DS-One SDHC (non DSi)
1GB Sandisk class 6 (I believe)
SnemulDS 0.6a WIP 2
MapExtMem = 1
Vblank- normal speed
Speedhacks- none
Works with or without EZ Flash 3-in-1 (using it causes slightly less stuttering, not required)
NO SAVESTATES EVER, loading these cause the levels to freeze whenever you change scenes
Select Auto SRAM saving and use ingame saves, should work and save perfectly
For the rom versions, I used the 1.0 of all DKC roms (if it exists)
DKC 1 and 2 should have the least glitches (if you set transparency to ON in the CFG). They are totally playable and enjoyable from start to finish and the graphical problems are not really bad at all. DKC 3 has some more glitches here and there, but is still pretty playable and enjoyable. The priorities for graphics do mess up here and there, but they're fixable. None of the games should completely freeze though if you are using ingame saves. Savestates are completely broken for these games. I suggest you delete the savestate files off your microSD for these 3 games as they are useless. You might want to delete your old ingame saves too if you want a fresh start.
As for other details, make sure you are using verified GOOD dumps. Here are the roms I use-
Donkey Kong Country (U) (V1.0) [!]
Donkey Kong Country 2 - Diddy's Kong Quest (U) (V1.1) [!]
Donkey Kong Country 3 - Dixie Kong's Double Trouble (U) [!]
I don't think the revision numbers matter much, but the [!] symbol is there to tell you that the game is verified as a GOOD dump, meaning there should be no issues with the roms themselves.
The last things I can suggest is to 1- delete and rewrite the roms and snemulDS program to the card. They may have become corrupted. My DKC rom somehow glitched up, but I fixed it by deleting it and putting it back on the microSD. Or 2- reformat your microSD completely. Make sure to back up all files on the card though before doing it. You will lose any data on it.