Why do you need a bed of hot embers, this suggests that your wood is not dry enough.
I had to use smokeless fuel when we had the log burner installed in our latest house, the seasoned wood we bought was not dry enough to burn and would only burn on a bed of hot embers.
We now get all our wood green and keep it for 3 years drying so we know what we have and where we stand. No need to ever measure moisture as you know its all dry.
I think you are measuring the moisture of the wood wrongly. You need to split the wood at the time of measuring and check in the middle of the freshly split surface to get a correct reading.
My suspicion is that most of your problems are down to the moisture content of the wood. I have never burnt Larch so can’t comment on that but I would have thought it should still burn ok if it was properly dry
The key to running a wood burner well and easily is a good source of wood that is consistent and correctly seasoned.