Oh love!
My thoughts for what they are worth...
You can have all the ideas and thoughts about what is best but if they are not working for you and your family then try something else. It's not hypocritical or abandoning your beliefs.
All through first pregnancy, I KNEW I was going to breastfeed because I'd love my baby so much I would do the very best thing for him no matter what. Oh yes. That was exactly what I was going to do. Until reality happened and I had a baby that couldn't/wouldn't latch on, midwives who looked at me in a puzzled way saying "well we don't know why he won't latch on" and me breaking down about three days in, bulk buying sterilisers & bottles. Yes, I could have persevered. I could have (in my sleep deprived and exhausted/emotional state) sought out a breast feeding counsellor (had I known that they even existed). But I looked at my content baby, happily suckling from a bottle and I just thought "ah balls to it". That's a prime example of someone seemingly abandoning their principles, but even now 11 years later I think I made the right choice atthe right time for US as a family. I didn't beat myself up about how I'd failed.
My list of what I swore I'd never inflict on my precious babies includes:
sticking them in front of a TV so I can get peace/get on with something
jar food
dummies
disposable nappies
sweets except for maybe once a year or decade or something
swearing in front of them 
I've done every single one of them and more. I still think I'm a "good" mum and the reason I think that is because I'm doing my best. I'm not perfect but I do the best I can in the context of what is best for all of us and that includes me. None of us are any good to anyone if we're racked with guilt and exhaustion about the things we've done. But we're operating in real life - not everything is as we'd expected or planned and so when we need to, we adapt.
You sound like you're being really hard on yourself. I think like a PP says you need to see if you can get a few hours each week to yourself - if you can stretch to a few hours in nursery then do it. I know you say I don't think I could put him in a nursery for just a day a week. I think it would be distressing for him because it wouldn't be regular enough for him to bond with the staff and err, because I'd feel guilty, which seems to be a common in theme in all my decisions at the moment but in the politest possible way, that is tosh. Babies are so adaptable - going once a week will become the norm. And believe it or not, babies like time with other babies. Think of your "guilt" another way - by getting a little bit of time to yourself where you can revive you will be doing him a favour.