"heat coming from under the dash (through the fire wall?)"
---either you have multible holes in the firewall---
OR
" am I just getting heat from the heater? I can't tell if it's shut off or not because the cables are stuck"
---More likely this is the case. The pull/push cables can be oiled (may take a while to soak in)
Even with the fan off...air is pushed thru the vent at speed.
Heater is easy to remove, clean-up, & that's a good time to clean/free up the control cables.
A quick fix is to "loop" the heater hose so as to by-pass the heater. air will still come thru but won't be as hot.
/emoticons/
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