Cutting all power off should reset t-stat , unless you have batteries in it , try it , but if outside unit not working after that ,a high pressure switch in o.s unit may be keping it from running
One end of this contactor should have 220+- volts on it with all power on to unit , when you turn on ac/heatpump the piece in the middle should pull in , (you may have two bars instead of one) , and you get the same voltage thru both ends of contactor is in outside unit as far as getting heat from heat pump , possible problems ; lo/high pressure switch = no freon,bad fan motor bad switch ,control board
If contactor does not pull in on heatpump with heat/cool on at t-stat with power on , you have a prob b4 outside unit
DO NOT FINGER TOUCH ANY METAL WIRING OR YOU WILL FEEL IT
The vents with no air coming out may be returns sucking air back in I hope.