Glad to hear about the recovery.
It's normal for them and many other wood catfish to assume all kinds of positions when in hiding and resting, disregarding which way is up or down.
As for the tank mates, our thread linked above features the community tanks our trachys inhabited, so some tank mate ideas could be taken from there. Ours have never tried to swallow a tank mate, except one time one trachy tried to eat a tropical gar and got the head in the stomach but nothing else.
koltsixx
reports that his trachy may attack tank mates very occasionally, like once in a few or more years. It likely is rooted in breeding urges and the instinct to bulk up for the season.