Do you have a decent backpack? I have a manduca (a bit pricey, but I considered it an investment in my mental health!! My baby was a lot like yours for a looooong time too). It is really comfy for both of us, and DD can sleep in it too. I'd often wear her around the house while I did stuff when she was being a cling-on. I also got some tall laundry baskets and will often put her in one while I do laundry (usually in the one with dry washing, but not always, hehe). She can stand in those and will often pass things out to me to hang out or fold. As long as I take what is offered whether I'm ready or not, she'll do that for a wee while.
Letting her roam around outside has been good too. Yes, she picked out a fair few plants that weren't weeds (sigh - she could have chosen from thousands of actual weeds!!) and I do have to hang around and keep an eye on her, but she thinks the backyard is a big adventure.
Do you have a cat/dog? My poor cats got a bit abused when I dragged them in to entertain the baby and she'd sit there bashing and plucking them but I think they'll be great friends in the long run, and these days she loves to chase them round and round the house.
Do you have a friend locally with a baby you can just go and hang out with and while the babies cause havoc together? Ideally one whose baby is as troublesome as yours, or it can sometimes make you feel worse! There is an OB mama that I hang out with sometimes and it's great cos she gets just how exhausting and frustrating it all is cos her boy is much like my girl. My coffee group on the otherhand, complaining about their babies that sound so much easier than mine, kinda wear me down a bit sometimes.
Dare I say it, but what about daycare? I was so, so miserable and hesitant about putting DD into care so I could go back to work, but now I'm SO glad that I did. We have an awesome centre who take excellent care of her and *parent* much the same as I do, I visit her at lunchtime each day, and she gets to play with so many new toys and other kids etc and she loves it. When she hops out of the car and realises she's in the daycare carpark, her little arms and legs get going and she starts squealing in delight. And, it gives me a break - yes, I spend it at work, but I have a job I love and I get to engage my brain and get refreshed to cope with the rest of the week with my grizzler. You'd get the benefits to him by going to playcentre, but daycare would let you get time out too which is not a bad idea.
I know how hard it is, I really do. Although I've come pretty close, I've made it to a (mostly) happy one-year-old's mum without getting PND. There are 5 things I think that have contributed to that:
1. My awesome DH - he's picked up so much slack around the house, and taken DD out so I could snooze sometimes and given me so much encouragement, even when I've been a grumpy monster.
2. The manduca - when I just can't deal with her anymore, I put her in a backcarry and put the stereo on and do some baking or go for a walk and she soons settles down and often even sleeps. I can still get something done, and honestly, sometimes being able to put her on my back where I can't see her is nice

I need the break!
3. Daycare and going back to work - some days I really feel like I suck at being a mum, and it's nice to go to work where I feel good at something. It's also nice to miss her during the day, rather than wish she'd give me 2 inches of space, you know?! And it's nice to know that she's getting lots of positive interaction from caring adults who have way more time and energy for her than I sometimes do. I also feel like I'm a better parent to her the days that I have her by having those couple of days off to recharge.
4. That stubborn, steely-will of hers is hereditary. She got it from me

. So if anyone can outlast the little ratbag, it's me!!
5. My mum. It took her a while to appreciate just how bad my girl is (I still don't think she really gets it, cos often she'd say "you had a bad night, you poor thing" when she's stayed the night, when actually, I've had a couple of 90-minute stretches which made it a good night by our standards!) But she certainly saw that we've been struggling and that DD was a pretty cranky baby, so she came to stay for a weekend once a month (she lives 6 hours away and works fulltime) and would clean the bathrooms, vacuum the entire house, do all the washing and clean the kitchen thoroughly so that in between times, I'd just have to do spot cleans. It meant that because things WERE getting done (just not by me) I didn't feel so frustrated having to look around me at all the things I couldn't do.
One last suggestion is find a medical person (for me it was my plunket nurse) to have a really good chat to about him, and just check that it isn't something *wrong* with him. DD recently got grommets to clear recurrent (read permanent) ear infections and she's so much nicer to be a mum to!
Hang in there hun, it does get better eventually even though it's very hard to live with at the time