Use the actual height of the antenna for your TVFR.
Effectiveness of indoor placement (ie attic) is hard to predict. There are too many variables to account for - building materials, local obstructions outside the building, loading/coupling/noise from anything conductive in the building - wires, pipes, etc. - and just the distance from the surroundings to the antenna. Typically you lose about half the signal in the air by simply being indoors and surrounded by a big box.
If you are doing ok with an indoor antenna, you will probably do much better with a proper outdoor antenna, located high outdoors in clear air and free of any obstructions between it and the horizon in the direction of the transmitters you are interested in.
Your TVFR is not very encouraging. Notice that WOWK is in a different band (VHF high) from the rest of the stations (UHF). You might be able to get it with rabbit ears if you are lucky and you aim the antenna properly. Rabbit ears can be made a little more sensitive to VHF with the addition of capacitive hats -
http://www.hdtvprimer.com/antennas/RabbitEars.html and
http://www.kyes.com/antenna/rabbitear.html