When the aorta gets above 4.0 it is called an aneurysm, and with that condition it is necessary to keep blood pressure as low as possible, and heavy lifting weight training raises blood pressure especially at the beginning of the exercise.
The current exercise routine shouldn't be a problem for a 4.0 cm aorta.
Those are great questions! Given your husband's excellent management of coronary artery disease risk factors, it must have been shocking when he was told he had a heart attack. That's the frustrating part of CAD. Despite all of his efforts, genetics ruled. The great news is, he survived, he is aware, and he is doing well! I'm sure he wants to just get back to his normal routine and doesn't consider exercise a potential trigger. However, because of the change in his aorta, I'd definitely talk one-on-one with his cardiologist to determine was is his best approach toward exercise. I hope you are both well and that you can convince him to double check with his doctor.
Take care and let us know how he's doing and what you find out. I'm sure other members would be interested in knowing the answer to your questions.
connie