Yelp, contact the police. Are you under police jurisdiction or sheriff? Whatever the case, I would inquire if an officer could ride out to your place. Explain to them that your husband will be working some awkward hours and the situation that you've just experienced...they should get the idea. If you are as remote as you've mentioned and the rode is a bit secluded then they might really want to know how to get back in there. And as, River Lizard mentioned...they could stop on the way out and visit "the boys"....certainly would do wonders for neighborhood relations.
Living in a semi-rural situation (main highway but can't see anyone's street light from here) we've been broken into once. The wife and I were at our business so it was easy for someone to know where we were...if they knew us. Otherwise it was simply a drive-by/opportunity-type of break-in.
It sounds like you can secure the major items in the barn pretty well...simply chain the quad and the mower together. Chainsaws and other small tools might be an issue....maybe construct a strongbox of sorts. I would be more concerned with house security...there's probably more (hand-carryable) valuables inside there (you've mentioned you have a gun(s)).
Security cameras are good, but I would put some phoney security system keypads up as well (just inside the house doors). A simple little box with an "eye", a blinking red LED, and a little "antenna" on it is another good project...could be positioned at the back of the barn. A few security system stickers on strategic windows.
If you have a loud stereo system....find a recording of a siren/burglar alarm and a nice looking thrown away remote control. Some alarm systems include a recording of "BURGLAR!!!, BURGLAR!!!, etc.,.. Mount some of the "blinking boxes" up where they're easily seen. One weekend blast the recording out of your stereo off and on (maybe 10 seconds each time) over a period of an hour or so. Maybe a few hours later sound it off another couple of times. Have the volume up REAL LOUD (speakers sitting in a window pointed in there direction). Be sure and have the "remote" with you. They *will* be curious and will eventually inquire about the noise....tell them you were setting up "the security system". If they don't inquire they will probably come to their on conclusion that you have a security system. Of course, be sure that they're at home when you "set it off".
Or, even better....install a real security system.
Best wishes,
Call the law,
Ed