I've often contemplated the same questions. I think it's clear on the hero X wings and you're right with that count.
The pyros are full of mystery to me. According to the first Chronicles book, there were 9 pyros made. I don't know if this is accurate or if it means 9 "high quality" pyros. You've listed 6 there. Are there 3 more good ones, or 3 more total?
There are also mid-range pyros such as the other Red 4 that we have photos of Joe Viskocil and Joe Johnston rigging for explosion during the Ep IV filming. It's of lesser quality than the high quality pyros listed above, but still nicer than some of the crude models that made the final cut of the film itself.