Hello and welcome.
It is true that you may still see the effects of the accidental 10u for a few cycles. You might find that once that effect wears off numbers will trend up, you'll just have to wait and see.
In any case you want to hold on to your 1u starting dose (unless he goes to low) for between 5-7 days if you are doing TR.
How much does Ovie weigh? Is he at a good weight? Dose is based on ideal weight of a kitty is to 'fluffy' or his actual weight if normal or under weight.
About the food...Lantus starts working aprox. 2 hours after shot....so you'll have to develop a feeding schedule for Ovie.
Us (and again, it's just us) we feed Toro 1/3 of food @ 1 hour after AMPS and 2/3 @ 2 hours after AMPS. He's usually out of food 4 hours before the next shot which works perfect to get an accurate PMPS BG reading. We try to duplicate the schedule during the night and get some BG tests then (especially that Toro has lower BG numbers during night).
So unless the AMPS or PMPS numbers are too low for shooting, we never feed him during or before the shot.
Other members can comment on this, I believe there are a lot of other feeding schedules used out there (some with automatic feeder involved, etc.). Different kitties, different schedules, different responses to treatment.....every cat is unique, that's the beauty (and the beast) of it.

Cheers.
I just wanted to make a comment on Toro and Ovi post, this is not the recommended way to feed
It is recommended to always
1) Test
2) feed
3) Shoot
I would most definitely not wait an hour after shooting to feed, you want to be sure that. Your kitty has some food in his system before onset, which with most kitties is somewhere between the +1-+2 mark. It can vary from kitty to kitty and from one day to another, over time you will figure out what is most usual for your kitty.
My feeding at +1 you are not giving enough time for the food to have its complete effect before onset.
It's also important to know if your cat is going to eat for you, as this might influence your choice of dose if for some reason he is off his food.
Fwiw I used to test, feed, and then shoot George while he still had his head in the bowl, most times he never looked up, the one time I tried to shoot before feeding (until a very experienced member set me straight) he would not hold still, he gets very excited about his breakfast
As far as how much and how often, eventually I settled on the following, he got 25% of his total intake at amps, 25% at pmps, then 25% divided into 3 snacks at +2+4+6(usually) in the am cycle, and the remaining 25% divided up just the same in the pm cycle (I use an auto feeder for that).
I tried to avoid feeding in the latter half of the cycle as it can have the undesirable effect of bumping their numbers up as there is less insulin around at this point to counteract any BG rise induced by food.
It is really important that you not feed 2hours before AMPS/PMPS as you don't want those BG readings to be food influenced so that you are sure it is safe to shoot.
If you absolutely must feed something at +9 because he's going to chew your arm off, or to avoid problems with acid tummy then either a little zero carb treat, like boiled chicken breast or freeze dried chicken treats are a good choice as this will not normally cause a food BG spike.
Of course of his BG is low, then ignore the above, as safety is what's important in that situation.