It is possible that manufacturer used some kind of Thread Lock one the thread. I would use a none marring pipe wrench or place 2-3 layers of ducting tape and regular pipe wrench.
It looks like you will need to use this rotating latching mechanism, most other latching knobs will very likely require different hole position.
Souhtco makes good of latches https://www.southco.com/en-us/
I like M1 series, it takes one finger to open and to close.