Type II and don't know what to do!

My 85 year old future father in law came to live with my fiancé this past Friday. About 3 hours after he arrived I found out that he has type II diabetes. I had no idea prior to that moment that he was diabetic and to say that I was a bit annoyed at my fiancé for not telling me is putting it lightly, since I do about 90% of the cooking.
He and his father is Honduran and though they both like all kinds of foods, I know his father is partial to Latin American food. I did sooooo much research of different recipes to make for him (as my fiancé knew), and it’s a bit annoying that he couldn't say “hey, while you’re researching what kind of food my dad likes…you might want to research what he can’t eat so you don’t kill him”. Let’s just say that it’s good I didn't make him a big ‘ol “welcome to Denver” pecan pie.
Yeah honey…thanks for the heads up so I can prepare.
He had to change health insurance, and now it will be about 3 weeks before he can see his new primary care physician. I've looked on the internet to try to get a better understanding of his general needs, but thought I’d ask a few general questions here as I know there are a few diabetics that use this site.
Just so everyone knows, he told us that he does not us insulin shots, he just takes a pill once a day (if that makes a difference):
He said that he drinks juice every morning and he drinks a kind that has no sugar added. I bought a grape juice (welches I think), which said ‘no sugar added’ on the label. I brought it home and he looked at the label…there was something like 30+ grams of sugar.( No sweetie, I’m not trying to kill you, I’m just a bit new at this) Of course I knew that fruit had natural sugars, but I didn't know that natural sugars would be just as bad as added sugar. He told me that he drank a juice that had only 2 grams of sugar.
C’mon old man, is that even possible??? (is what I wanted to say but didn't)
If so, does anyone know what juice it is?? I asked him and of course being 85, he doesn't remember the name. He just knows that it’s not in the refrigerated aisle but in the regular juice aisle. I plan on taking him to the store when I get off work and having him show me, but I’d rather not drag him in the store if I don’t have to.
Are there any foods that he shouldn't eat? He says he can eat anything including regularly made desserts as long as it’s a small piece and it’s not a daily thing. Is this true? I don’t want to make a pie, give him a piece, and he gets all sick!
I know most of you are saying to talk to his doctor, and believe me I will. It’s just that he’s pretty strong willed, and even if the doctor says he shouldn't, if he says he can then that’s what he’s going to expect us to do.
In other words, if we’re walking through a store and he wants a snickers bar and he hasn’t had any other sugary things in days, is that OK? Or if we’re in a restaurant and he orders a slice of pie, should I embarrass him like a 5 year old and tell him he can’t have it, or if it’s every once in a while is it OK?
This very moment, my fiancé is on the phone with his dad’s old doctor’s office in New Orleans, but getting a hold of this doc is proving to be next to impossible. In the meantime, I’m hoping that there might be a MFP or 2 out there that can help me out. Thanks!!

TL;DR- My father in law is diabetic and I don't' know what to feed him.