I'd really try to make some of these, the SALT and a couple of sessions of the courses if I were you. But do try and change the times. I wouldn't have thought missing the second day of nursery would be too bad in the long run.
I'm in a similar situation. My child, 4, is only just being formally assessed. But I'm really busy with a kind of 'ABA/SALT/OT' set up I've tailored, part time work from home etc. It's working well and I've practically taught myself so much in the last year that I have ASD coming out of my ears.
I paid for OT, and SLT last year, but even then I was shocked at how much more I knew than they did. I hope that's not arrogant, as it made me feel really worried. How on earth did I knew I more when they were fully qualified? It was all generic one size fits all advice so I didn't pay for anymore and just got on with it myself.
And yet I did get to learn a little each time. Either confirming, after trying what SLT had said, that I was doing something a bit more tuned in, or by asking good questions, getting a little more insight or the odd practical tool that was useful.
Now I'm about to get, eventually, a little NHS treatment. And despite everything, I still think it's good to keep trying to ask any experts for advice, to get their perspectives. Even if it's not very effective, we have to try. And also, no matter how 'good' we are, if we are doing ABA ourselves as parents or such like, I do think it is healthy to check in with other professionals as otherwise we may be missing stuff, or being too intense. Too easy to go into our own isolated silo's.