Hello .. if you wish to remoove the garage switch , then some modification there is needed
this quote .... "connect the hot/live wire from line to black wire and (same for load) to blue wire... meqans that you connect your black house power wire to the switch black wire ... that should be the black wire that was on the common of the old switch
then the white on the switch to the bundle of whites in the box ... and green to the group of green wires
Now we need to figure out where the wire to the lights is, in which switch box
I think in that inside switch box you have a black and white wire connected together
and in the switch box in the garage the white is on the common of the 3way switch
could you confirm these for me please
OK .. if the garage switch is black, red , black , then the power and lights wires are not in the same switch box
I will add a sketch
at the inside switch connect the blue switch wire to the house red wire
and at the garage switch , remove the switch and connect the black that is on the common to the red wire ...
you will need a blank switch cover for this box ..
the top sketch is what I think is existing from your description ,, and the bottom is with a single pole switch in the house and no switch in the garage
any thoughts , concerns ??