Just for the record- I read the whole thread. This is insane. I don't blame you for being discouraged but it's time to try something different.
You deserve to have your horse back. Plenty of cowboys hate horse thieves enough to help. Sounds like some other people here do too. Don't go alone, but definitely go get Max. Safety in numbers applies here. You want witnesses/lookouts with you at every step of the process. It's better to celebrate together later - than end up scared off or shot with no horse and lack of witnesses. These law officials are either inept, dishonest or family/buddies. So, you need to do part of their job. Just carefully.
You said he has a few properties. Do you have the addresses of them?
A private investigator could probably get you the addresses if needed, but I bet you could find them yourself. Deeds are public record, and so are tax assessments. \\
Google his name and and his business/farms name to see what pops up. Check for a criminal record too. Might get lucky - and get an address, pictures or just more familiar with your prey. Too catch a sneak, be a little sneaky yourself.
He deserves for you to make a good case against him, retrieve your horse, and still prosecute. Sounds like Oklahoma's livestock laws need work.
Here's some ideas that might help narrow down your horses location:
Mapquest the area, streets or addresses. and see which ones have rural/ag zoning. He probably would not have a horse downtown, after all. Pulling up a map of the general area would give you a starting point.
Type the more likely address(es) into Google Earth and have a good look at the neighborhood. It's easy, and a safer way to case the place. A computer geek can find so much. You can check this for FREE. They have fancier upgrades you can buy , but you don't need to.
If any of the properties are for sale- you might get pics, topo maps, or at least a description and directions online, or by having a real estate person e-mail them to you. Use a name that wont be recognized if you need to give one. Preferably a guys name since they know a woman is after them.
Print the picture and make copies of it so everybody involved knows where are the best surveillance spots, the STABLES/BARN, blind spots, etc.
See if it shows the fence lines, driveways, and any safe exits from the property. Once you have him- you want to get away safe and quick.
The map might show vehicles. Note how many, type (car, truck, van) and color so you know if they are gone easier. I wish there was a way to know if he has any local enemies. They might help you - just to screw him.
You're welcome to PM me.