Ok, first of all he is at a huge risk walking around with a pressure that high and a bad family history.
If i had seen your husband (I am a cardiologist) I would not have let him leave with a trial of a medication. We do that when people do not have the risk factors he does. It would be wiser to admit him for 24 to 48 hours and bring the pressure down before he leaves the hospital.
Its true that it can take a while for the pressure to come down but the important thing is it doesnt have to be that way.
I dont want to imply anything bad about your MD, but alot of times docs will start a medication and see the patient back in a few weeks just because their schedule is too full or because the insurance will not cover two visits in a short period.
Not knowing much else about his health, other things being normal I would have started him on a beta blocker
and an ACE-Inhibitor or an ARB agent with a mild diuretic
Get your self a Good BP measuring device. I mean a good one as it looks like he will be needing it for a long time (frequent home checks) A and D Medical makes a good one. model number UA-767 plus BT. now that one has a blue tooth capibility, which you wont need so look to see if they also make one without the BT, or if its priced right just get it. Most of the good ones are around a hundred bucks. Dont get the wrist ones as they dont work well.
I hope this helped, if you have any questions just e mail me. good luck and make sure he see's someone right away