The good news is UNIX (and of course Linux) has a standard mechanism for freezing and unfreezing processes:
$ kill -STOP
(from another shell)
will stop the process. It will still reside in the memory (RAM or swap).
To continue process, from the shell where it was started, type
There will be no echo, but the command will execute.
If there is an echo, the tty is probably messed up. It can be restored again with
$ stty -brkint -icrnl ixoff -imaxbel iutf8 -isig -icanon -iexten -echo