If that is what I said, would your answer have been "Yes"?
Am I using the correct ports (9153 and 9154) but the wrong address? (127.0.0.1 as opposed to 10.152.152.10?)
Wrong address, yes. Plus, btw in case of Qubes. you need the IP of Qubes-Whonix-Gateway.
In the workstation…
Why are they pointing at localhost by default if there is no tor instance there? Are you rerouting it to the gateway somewhere in the worstation?
Explained here (see footnote):
The default (first) Tor Browser the workstation being able to use 127.0.0.1 is only a workaround, so we do not have to modify Tor Browser itself, because this is very difficult (fragile) from a distribution perspective. That way Tor Browser works out of the box without proxy settings modifications for most users in most cases. No matter which way installed (ex: tb-updater or manually).
Where am I supposed to be pointing things like Pidgin?
From the stream isolation page...
"With IsolateDestAddr and with IsolateDestPort: SocksPort: 10.152.152.10:9180 to 9189"
(Qubes-Whonix-Gateway IP instead again.)
(For a messenger the options (IsolateDestAddr / IsolateDestPort) are okay. For web browsing not. (Also mentioned on the stream isolation page.)