Great question. Management of atrial fibrillation is a long and complex topic, mostly due to variations in patient population, preexisting medical conditions and available medications. As far as I can tell, your husband is a healthy 49 year old with occasional short runs of atrial fib - what we call paroxysmal + lone atrial fibrillation. Usually there is very low risk of cardiovascular risk such as a stroke in this population; however, it should not be completely ignored.
I recommend at least an echocardiogram to confrim heart muscle and valve function (if not already done), AND a holter monitor to confirm his "afib burden", ie.find out how much atrial fib he is really having -- those he can and cannot feel.
If after these tests are done he truly is CHADS2VaSC = 0, risk of stroke is very low at 0.78 per 100 person-years. He might choose to NOT be on any stroke-preventer. IF he were my patient, I would recommend aspirin daily -- usually a full 325mg dose is recommended, although 81 and 325 mg doses have never been compared head-to-head in a large trial. So if dose of aspirin is a concern, try 162mg.
I meant to include that he does take ibuprofen nightly. If he decides to take aspirin it would need to be 30 minutes prior to the ibuprofen or 8 hours afterwards, correct?