If you have some money to spend. I'd suggest one of two:
1. Upgrade to professional + DBS + Boosters. That will get you 4G video + HD live view. And it can go 3+ miles easy. If you want to inspect crops, HD is helpful.
2. Add boosters to your DBS. There are devices that you can add between the antenna and the remote. They electronically amplify the signals. If you are flying above a farm with nothing blocking LOS, I believe they will be very effective.
The thing you should consider is that once you add boosters to the 3 connections you spend another $150-$300. When you add up the standard + DBS + boosters = $800 to $950. At which we know is more expensive than the PRO.
On the other hand, if you can't return it and want to mod it for maximum distance, boosters would definitely be a viable option.
Edit; Also, the DBS is very directional. You have a 30° angle. You must hold the remote with the antenna pointed perfectly to the bird. I've had my antenna shift from red to green at 5000ft because I angled my antenna slightly. The Sunhas boosters should fix that problem.