PottyTraining: Give up?

I have a 2.5yr old boy. He has potty training for what seems like forever now. About 5 months now. He has had some very good days where he would run to the bathroom and pee/poop and not messes. The best he has ever done is 2 days no accidents. But for the past month I feel like he is just not trying anymore. He came with a pull up (they live 45mins away so he needs it for the car). As soon as he came I askedd if he wants to go pee or poop (he is a notorious morning pooper). He say "no thanks". About 15mins later I ask him to go try anyways, he says "I don't need to go...." then I get the 'whiff'. He had already pooped in his pullup. Argggg. Okay. No biggie. I remind him that we should be going to the bathroom if he needs to poop.
Fast forward our morning. We played outside, walk around the block, water table, came inside while I made lunch. I ask him a couple times if he needs to go, always says no. We sit down for lunch and before I seat him I remind him again to go to the bathroom if/when he has to go. After lunch I am cleaning him up and see that his pants are soaked and a puddle under the chair. I am getting so frustrated with this!!
I am about ready to tell mom that I am done until he is ready to start trying himself.
Also, should I ask the mom for diapers instead of pullups, as I find they are easier to change, especially for poops and can be wrapped up for disposal.
Any advice?? I have potty trained many, many kids but this one is getting me so frustrated!!

If he is in fact toilet trained, then he does not need a pull up in the car. Mum or Dad need to put a potty in the car and a big bottle of water to rinse and if the kid needs to go, he should be asking and then they pull over so he can go. This is laziness and is clearly having a negative effect now.

As for when he arrives and then he pooped in his pull up...the pull up should have come off immediately upon entry to daycare. Kids aren't stupid and he knows he can get away with soiling a pull up because it is a glorified diaper, hence why I do not use pull ups. He should be in underwear at all times except naptimes if he isn't able to go that extended stretch asleep yet. Eliminate the pullups on the drive over first of all, if he has a regular BM in the morning, then only ask him once to go and if he declines, tell him he has to go and try a few minutes later.

I would nip this in the bud now by maybe making regular toileting breaks more frequently and not a request, just to get him back on track if he isn't doing a great job at remembering to verbalize his needs or is showing resistance upon request. The pull up though after 5mths of being trained is probably not helping matters but otherwise all kids go through digressions. Hopefully he will get back on track quickly.

I don't ask I tell! Here we all go at specific times. If they don't say they need to go any other time then he is not ready. I would stay in pull-ups though and not go back to diapers.

During potty training, they are told when to sit on the potty, I don't ask them as this implies they have a choice. They also obviously sit on it when they request as well.

Once they are fully trained, I ask them as they now know if they need to go or not. The only time I make my older kids (both 3.5 yo) use the toilet is before nap and before going outside.

The girl I am almost done potty training is a notorious after nap pooper, so I always make her sit for a good length of time after nap and 90% of the time she poops. She is getting good at peeing on the potty without being prompted, but catching the poops is still a problem for her. If I knew that a child that I was potty training always pooped in the morning I would make it part of the daily routine to have them try during that time. Give them some books to look at (or something) and have them sit for awhile so they can relax their body and let it come out.

But yes, I also agree that the pull ups need to go if you have been going at it for 5 months already. He needs a push to have a reason not to just go in his pants.

When potty training I tell also I never ask.... And yup take the pull up off right away and onto the potty then undies (the thick ones) ... If he has been doing it fine and now he's going in his pants then he knows better and he's making a choice to go in his pants rather then in the potty/toilet .... It's not an accident it's a choice !

I require pull-ups here and do not allow underwear until I approve it. There needs to be 2 full weeks of no accidents. I also reserve the right to go back to pull-ups if the accidents become too frequent. I don't have time to constantly clean up messes on the floor! I would however never go back to diapers.

Children here are sent to the washroom at certain times of day. I not ask. They told to all go. If they need go in between, then they go.
No pull up when toilet trained. Too confusing. They either in big underwear being toilet trained or in diapers not. No back and forward.
If someone very new to toilet training had very long journey in, then I can understand need for pull up at first but it need to come off immediately they arrive.
There too many mixed message in pull up feel like diaper, pull up in car, pull up after arrival at day care - yet 5 months into toilet training! Too confusing. It say to child that sometimes, it okay to pee/poop in underwear but other times of day, toilet is used. No consistency in approach = no consistency in result.
Once toilet training begin, I never consider it an option to give up. It takes some children longer than others but there is no stage of development where I would expect child to give up walking, talking, trying to pump their leg ans make swing go themselves, eating with spoon independant, or anything else. Why people think toilet training is okay to quit I not understand.