So if it were me, I'd be running between 500 and 800 watts
But that's just me

Try what flipzed suggested

And I agree with jorjef
We do acclimate much faster than 1 degree per hour, so set them and let 'em go

Think I figured it out. Seems that there wasn't enough flow passing past the heater.

I went three to six months without a heater. I actually unplugged my heater at some point before... Probably thought it was a powerhead.

I never even noticed. And because my house is always warm cause of the baby, there was zero losses and nothing bad happened. Tank was at 72.

I plugged it back in and let it heat to 78 over the day.

Sounds like good news