Oh Amber- ya poor chook. Sleep deprivation is cruel form of torture.

To begin with you are doing a great job. As you said he is a happy boy.

Our sleep has been really on and off lately. It's tough being 9 months. In our case, they are on move, learning so much, trying to walk, learning to talk and on top of all that they have sore gums, sore ears, the list can go on!
Not sure if M is teething, but our restless nights seems to conincide with a tooth. (Which has been ongoing since 5 months! )
You have done so well to get him doing a stint in the cot. Baby steps. He will improve. Does he come in when DH leaves b/c he wakes him up getting ready? Will he not be settled in his cot? Co-sleeping is great if it works, but it doesn't work for us. We continually wake each other up. And she needs resettling every sleep cycle. Where as i find in her cot, she sleeps much longer. If he is sleeping better in his cot, can you put him in the cot in your room, so you don't have to go to far to settle him?

We only have 3 x 40min sleeps some days. Sometimes it is only 1, 1.5hr sleep!
Not ideal, but i don't stress about it, i just try and encourage longer sleeps. When she first stirs i often pop in and pat her back and she'll sleep for another cycle. But not always.

Like 'No cry' says. If your new method isn't working, go back to the old way, but try again the next time. It may take a few weeks, but they will learn.

It will get better. Truely. I am hoping once Lu is walking properly she will be so exhausted she sleeps all night! Here's hoping anyway!

You are doing a great job, you really are a loving and caring mum, and it will pay off. don't doubt yourself, keep up the good work.