I'm afriad that because your dad just had a stroke, most of your advice must come from his medical team..
There are quite a possible list of reasons why his BG has increased over the week
Stress, he must be pretty stressed after suffering the stroke both mentally and most likely physicaly, so this would increase his BG (mental stress can increase as the weeks gos on, due to what's happened sinking in, and starting to fear it happening again)
His activitiy levels could have decressed enough to cause his BG to raise
If they are given him medications to help or treat the after effects of the stroke could be increaseing his BG's..
He might be coming down with an infection that causing his BG to increase..
It sounds as though he needs his insulin adjusted to meet an different need, which you will need the advice from his medical team to best adjust this..
But under the circumstances of still in the very early recovery stage of having stroke, and his blood glucose being so high, I would call the out of hours doctor requesting a visit or even try to get him back into hosptial... As his levels could cause ketones and DKA (if you've got the ketone sticks to test I would advice you to test) any sign of them get medical advice, if you haven't and he shows any signs of being unwell then again get medical advice.. As he's got enough on his plate without adding DKA to it..
I would also on monday morning phone his doctor (or hospital contact if he's got one) and start pushing for them to be more active in there approach to his after care reguarding his diaebtic care as well as his stroke treatment..