I can't comment on the tuner card and streaming...no experience with that.
It looks like you have some good strong line of sight signals from the southwest. WSB seems to be the only major that is not located in that direction. Maybe you will be able to pick them up off the side of your antenna with no problem. You will just have to try it and see.
You probably should not even consider an amp of any kind until you have your antenna installed and tested. Too much amplification in the presence of strong signals will actually make things worse. The signal loss over 50 ft with good quality RG-6 coax would be 4 dB or less.
When it comes to combining antennas, that can be a problem without using specially made filters to combine the signals. Two antennas connected together without such a filter can have signals arriving at each antenna out of phase with each other and cancel each other out. If that is the case, one solution would be to have each antenna connected to a separate tuner card.
What type of antenna are you looking at? If you want WXIA and WGTV, get an antenna that receives VHF-Hi in addition to UHF. Best of luck!