I use the limited set of the software, available under TC, and I see ~/.cache directory and see it being used by some software, but I've never seen caches in /tmp. I propose You the following sequence of RAM saving steps:
1. Persistent /home and /opt
2. Using real swap on the hard disk and "nozswap" boot option
and as the very last
3. Moving /tmp somewhere else. I can not say exactly step by step how this can be done, but You will need to rework system startup files very thoroughly, otherwise You'll get system disaster.