Okay, so first of all: does your city not have public transit, or is your work or home not on a transit route? How much walking would be involved to get to a transit stop? I ask all of these questions because one of my brothers has never gotten his driver’s license and spent years walking everywhere in the city he lives in (at one point it was uphill to get to work every day, a trek that would have taken me well over an hour; I don’t know how long it took him) so he didn’t have to pay for a bus pass (he’s very good at saving his money). This includes in the winter with snow and wind and everything else in a good Canadian winter.
Your work shouldn’t affect your medication, but it might; the thing is, the activity should actually be helping your focus as well, so if anything you should be having fewer problems. What kind of meds are you on? If amphetamine-based, remember not to drink fruit juice while it’s active in your system, because that will diminish its effectiveness. Also, are you getting enough sleep? That can impact how well your medication works. Same with how much stress you’re under. Lack of sleep, stress, and poor diet all can cause ADHD symptoms to be worse, which means that our meds seem to not work as well anymore. I’ve explained this phenomenon here.
I personally think you should talk to your parents and tell them that if they want you to get your license before they go, they need to pay for you to take actual driving lessons with an actual professional driving teacher. That will probably help a lot, since the professional won’t freak you out with constant criticism.
Also, what if you got your license and then only drove to a transit stop just inside the city and then took the bus to work? It might take longer and you might have to pay for parking. But you wouldn’t have to navigate so much of the city in the van, and that would be better for your mental state.