Abe,
You have a bit more flexibility in adjusting range with output power on a VTX (airframe), but a poorly setup VRX (ground station) will throw most of that power advantage away. Loose connections, mismatched or poorly tuned antennas and insensitive/noisy VRX's will hurt your range just as fast as too low power on a VRX. Choosing directional antennas (particularly higher-gain-narrower-beam antennas) or switching to lower frequency bands (1.3GHz, 900MHz . . . ) when you move out in range will dramatically improve how far your ground station can hear.
BTW, about the video . . . FPV video stinks. It always has. It's serviceable to fly from, and when you're in the air, you'll ignore the lower quality, but it's rarely pretty. If you're going out with the purpose of taking photos/video of production acreage, have a second camera onboard for that capture. The FPV gear will help you get the airframe in the right spot and frame up to "get the shot", and give you a little instant feedback, and when you land you'll have higher-quality images to evaluate the crop trials with form the nicer camera.
One other thing to keep in mind . . . your ground station doesn't have to be back at the house. So long as you have a suitable launch/landing site, you can drive right next to the field and launch from there, and save yourself the headache of commuting via FPV. That gives you less delay between launch and work, more loiter time over the target, shorter ranges and less airspace to loose your airframe over when something goes wrong. You already have vehicles that can carry gear to the field, make them do the tedious commute for your airframes
