OP, I am bipolar and have had PTSD (well, I've been in therapy for a long time, so it's a lot more diminished. I still have anxiety which is better and worse at different times.)
So in my totally biased opinion, no, you are not wrong to be in love with someone who's mentally imperfect. There are lots of mentally imperfect people about, and lots of us can also be quite lovable.
If my child had bipolar, I would like to think that they wouldn't have to go through life alone.
With regards to your situation, I think you're not unreasonable, but I think it's worth taking stock every now and checking that you've got your eyes completely open.
The fact that your DP accepts the diagnosis and is getting treatment is wonderful news. It's really commendable that he's comfortable and is doing what I know is extremely hard work to better his situation. It is serious work.
With regards to the medication and no side effects, it's worth knowing that sometimes with these meds (depending on what they are) side effects are not always as instant as they can be with other drugs. I'd been on mine a year before I realised I suddenly couldn't produce enough saliva and was struggling to swallow. I reduced for a bit and it cleared. It's also worth knowing that there's a really irritating catch-22 with these things, in that often, when you feel you really want to come off them, it's because they're not working properly. So rather than coming off, you need to have them reviewed and either changed or increased. It's one of those irritating things that I know for sure when I'm 'well' but I'm convinced it isn't right when I'm not. It goes with the territory.
His dose may well need adjusting from time to time. Mine is varied by 50mgs through the month. There are days I need less, there are days I need more. I was fine for the first year before this variable increase needed to happen.
In his care plan, it's worth putting in support and breaks for you. Particularly when he's recovering from a 'blip'. It's hard work. I'm horrified when I think of some of the things I've put DH through, though he manages it very well (he finds it fascinating, and he loves me). It's important to us both that when he's able to take breaks, he takes breaks. He goes to stay with his mum in London and kicks back and goes out with his mates.
The children know that there is something wrong with Mummy's brain, and that she's working with lots of doctors and nurses and because of that, we're all fine. I'm fine to go to work and to pick them up from school and to do homework and play with them. Sometimes I do things just because my brain is 'fizzing'. It's important to me that afterwards, we identify them and explain. I had a bad spell the other day - a really short one, 90 minutes for the bad bit - and afterwards I was able to point out how Granny had looked after them and my sister had looked after me until we were all well - that's what happens in our family, and it's OK. The school know and the children know who to talk to if they're worried.
Finally (sorry for the mega-post), your mum probably reacted with shock. My MIL reacted with shock and fear, and then quickly read up, learned stuff, and got on board with what she might need to do in certain situations (not a lot, in fact, but the list of emergency numbers are on the fridge, so that's worth her knowing).
All of this makes it sound as though we're constantly living in fear of this stuff. We're not. I'm looked after and medicated and we have a lot of plans simply so we don't have to live in fear. These days it's problematic for me only for a couple of days a month, and I manage that quietly by myself, and problematic for other people for maybe an hour or two every month or two if that. The bad spell I had the other day was the first one in a long, long time.
So good luck to you, and I hope it all goes very well!