Dalby is a stacked loop design so it’s easy to break down into “pieces” to fit time and inclination.
So far as I know there’s no direct link between the toll road fee and trails, some money goes into various bike related stuff (Rangers, resources, materials, etc) but whether it’s more or less than what’s raised by bikers going to the forest I don’t know. Then again there’s a lot more to Dalby than the MTB trails (although you do have to pay for some of it – cafe, Go Ape etc).
Dixons Hollow was designed by Adrian Carter (Pace) with input from the FC Engineer and was based on bike park style features Adrian had seen abroad, AFAIK. It’s quite an old design and had to fit with requirements of the area and money etc etc. I doubt anyone would argue it’s perfect, but recent rebuilding of the jumps has got to be a good thing (IMO). It has certainly proved popular for certain groups / users. I imagine it could be improved and with hindsight designed differently but that’s true of many things, not just trails. Time consuming and expensive to do so.
SingletrAction built a wee pump track adjacent to Dixon’s last year and that’s proved quite popular (although possibly rather misunderstood ;-).
Dig days in general have suffered from really poor turnouts. Mind boggling really when you think how many people go through there and use the trails, but hey ho, that’s volunteering for you. Efforts are re-starting so if you’re interested visit the SingeltrAction site, ask on the forum or look them up on Facebook.