Model FTXS12LVJU. Are you saying run it in auto mode? I've been running it on cool mode, medium fan speed. Remote temp setting is at 64, low as it will go.
I found mine run best at the medium or high fan speed. I never use the auto fan setting. Try setting the fan to high and I would set the remote to 66-68. That works best for most wall units in cooling mode. If it's too noisy set it to Medium.
At full output your unit is rated at 23 seer but when it's running at low speeds it is probably running at 40+ seer. A typical central air unit is 10-16 seer for comparison.