I'm coming in a bit late here, sorry!
A couple of things - are you already in an HRCAV club? If not, you want me to list the ones near you (you'd have to tell me or PM me your location)? You could contact them and ask them if they know an instructor who could help you with groundwork (something you can do while preggers).
I reckon it would be worth giving Ross Jacobs a call to see if he'd come down to you and help you with one or both of your horses - I've seen him work and he's great, though expect to be a big part of the session!
I don't subscribe to the idea of number of falls equating skill at riding! I think the aim is to reduce your falls and keep them to an absolute minimum - I had a massive fall when I was first learning to ride properly on my first horse and I've only had a couple of silly small falls since because I absolutely REFUSE to come off! Concussion for a week is not fun, so I make sure I'm sticky...
I rode till 28 weeks last time, and only stopped cos of my SPD, but as I'm back into my yoga, I'm hoping I can make longer next time. If you feel it's too risky to ride while UTD, best to keep off - something I'd only recommend if you were confident in your horse and your abilities.
My horse is 3/4 QH and is similarly lacking his 'go' button! I'm confident riding him whilst UTD because the issue with him is getting him forward, not pulling him back. That and I'll be sticking to arena and small paddock work next time again. And DS is starting to ride, so I can lunge him to keep pony in work
Let me know if you need any of those contacts.