I think the F0 F0 F0 is a symptom of the 8th bit being stripped. Try switching to the AM65A or even the AM65AX. I can't remember the exact difference between those but one was meant to support 8 bit extended mode. As a test, set the ZTERM configuration | international option to 8 bit Latin1, and try writing a one-liner program something like this:
PRINT CHR(225)
If the 8th bit is passing through properly to ZTERM, then you should see the accented character à. If not, that implies that the 8th bit is being stripped on the way out, either by the interface driver or by the terminal driver (or by something that hooks into them, like TRACKER or MULTI).