How do I keep the neighboring Remote Control Airfield from flying over my property?
I'm surprised that all the answers and comments so far have been about resorting to laws, other higher authorities, or anti-aircraft batteries, and that nobody has suggested being nice.
When you say that you approached them to stop and they refused, that sounds like you went and talked to people flying their RC planes.  Presumably the RC airfield is leased by a club, which is probably legally organized as a non-profit corporation, which therefore has a board that meets regularly according to bylaws.  In ordinary times I would suggest finding out when the club board meets, and paying them a visit.  (With the pandemic stalking the land you're probably better off telephoning the club president or other club officer.)  If you appear at the board meeting and identify yourself politely and state reasonable concerns without accusing anyone personally, then I would think most club boards would take your concerns seriously, raise the issue with the rank-and-file club members at the next regular meeting, put a strongly-worded notice in the club newsletter, and give you telephone numbers of several board members to call in case you have any more trouble.
Most clubs devoted to any hobby just want to pursue their hobby in peace, and in order to be left alone they need to be good neighbors, and so that's what most clubs try to do.  It shouldn't be hard to get people to not fly over your property and close gates after they retrieve planes that accidentally came down on your land.
Then there is your demand that they not fly planes in your view.  Are planes over their field in your view?  In that case your demand may be neither legal nor reasonable.  (Please know that I'm no lawyer.)  Even so they may be willing to negotiate if asked nicely, and for instance offer to fly only three hours a day for two days a week just to avoid trouble.