Hi Sandra,
It would be good to get him seeing more green.
I can't help feeling that the way you are feeding is impacting his cycles. I know you have multiple cats and understand how difficult that can be, we have George and 3 civies.
We know that when we feed in the latter half of the cycle (so that +8/+9 meal that you regularly give Buddy in the mornings) this can often bump the PS up, basically you are feeding when the insulin is at it's weaker part of the cycle, and this can do bump numbers up and shorten the duration leading to a higher PS.
To get the lovely flat green cycles that lantus is famous for, you want to avoid those higher PS.
I used to feed amps +2 +4 +6 pmps +2 +4 +5 (I normally went to bed midnight that was +5) I tried to keep the food symmetrical as possible.
What time do you shoot? I see you often get a +4??
Maybe a amps +1 +3 +5 pmps +1 +3 +4 might work for you? allowing you to get your normal sleep time.
I'm not suggesting you feed more just divide it up differently and more evenly. I think this will help balance up am and pm cycles and see him flatten out more evenly during both cycles.
Another thing to bear in mind, is that even if Buddy does end up going OTJ most kitties do a lot better with regular meals throughout the day. George now he is OTJ gets fed every 3 hours (I use an autofeeder) and I have to keep him separate when I'm in bed, not because the other cats will eat his food, but because he will eat their food, they graze, and he's just a glutton.
I have noted that on days when he misses his snacks, because he is now deaf and doesn't hear his autofeeder, his BG is higher than normal in the mornings.
However when he was on insulin I didn't usually feed past +6 (unless of course I needed to because of his numbers)
I really think that it would be worth trying a food experiment and seeing if it makes a difference for Buddy. I know what a pain it is to have to separate them, I wish I didn't have to. We even tried giving the civies access to food in another room via cat flap, but my little girl refuses to use the cat flap

. So in the end we've had to separate them.

but we do it because it helps with Georges BG, in the end they have all got used to it.
If you do decide to try changing the food schedule, do that for a few cycles before taking the dose up. Best not to change two things at once.
Give it some thought.