It seems the amount of interference I am picking up is more with using the antenna daisy chain as opposed to independent systems.
How is the interference manifesting itself? Are you actually getting dropouts or just interference? Well the antennas are dumb ... that is they just pick up any RF in their bandwidth. So if you have better antenna coverage you will also be picking up more interference as well. The advantage you do have using the directional paddles is that hopefully you can set their dead side to known interference (such as a wap). You are kinda cheating by only using one paddle and could probably avoid more interference by using them in pairs ... YMMV. Interference by itself doesn't really affect the audio so until you get too much there really isn't a problem. It is normal to get some (maybe lots).
Am I doing something wrong here? There are four BNC jacks on the back of each receiver. Starting at the top I am taking the Antenna jacks on the far outside of the receiver and connecting them to antennas and then taking the inner jacks and connecting them to the outer jacks on the receiver below it and so on. Am I doing this correctly?
Sounds correct. As Robert pointed out, terminators are a must on V70 and should not be used on V75.
Is there any advantage/disadvantage to using the different gain settings on the paddle antennas?
You don't want too much gain as it becomes problematic. Take a look at the RSSI indicators (the triangles on the receiver's LCD screen). Don't turn up any higher than it takes to get 4 bars on them. It's usually better to be just on the low side than just on the high side.
I'd add one more thing ... check the condition of your coax cables. Coax cables are relatively fragile compared to mic cables. Kinks and bends in them ruin them. So does running over them with a hand truck. If this is a portable system consider then expendable.