Um, I only counted two pages?
Interesting read, nonethereless. Yes, it does sound feasible, I can tell you've put some thought into it.
The three significant ways it differs from my cunning plan is I think we can do it entirely off our own back, and plotted a slightly different route to get there - namely launching a seed factory and using (mostly) LEO debris to expand and clone it. From there throw the clone out to the Mars/Jupiter belt... Let the resources come to us. Whilst that's happening LEO cleanup efforts should of enabled facilities on the other side of the moon ready to start doing things with the incoming resources... preferably orbital farms - conventional and energy - to both support our population and for Earth, then with supply chains firmly established work on housing the population.
The second is once infinite resources have been established, we should just give Earth everything it needs(as opposed to the selling we would of been doing to self-support) and thusly end world hunger and poverty.
The third is politically, some of the responsibility should fall unto the technically qualified - but at all points the actual decisive capacity to retain to the individual citizen. This should allow the entire infrastructure to move in all directions with enthusiasm tempered by sane guidance and ensure it's never in a direction the people wouldn't want to go.
A few things I phear you failed to point out with your model(and mine) is by moving industrial processes into orbit you can safely contain pollutants. Anything that cannot be reacted with something else to make something useful can be centrafuged into Sol. It should incinerate long before it gets there, and pose little issues to the star. It'd also open up for waste disposal capacity for Earth - they seem to be making a lot of things they can't get rid of, and are simply stupid to have lying around. Another is with an orbital grid beaming down to Earth, it should be possible to reach incredibly competitive prices for delivering energy. Setup is costly affair - but if that's by resources obtained from the belt, all it really costs is time. Maintainence is an issue for some technologies, like solar, a hadoop-dyson loop that someone suggested somewhere interests me... but even solar should be do-able - again, resources from belt makes that incredibly cheap to replace burned out units, or ones that still feature MMOD strike where we've not quite got it all yet. Competitive delivery can force Earth away from it's more destructive generation methods, and improve everyone's quality of life.
A strong foundation will take years to construct to enable a population to exist on space colonies, to eventually consider migration from Earth to become an island in space leading to founding a new home world to take the next step in human evolution.
That, however, I see as over-optimistic. Not years. Decades. I also think one island isn't clever - that's a single point of failure. To be able to build that island, we're gonna need infinite resources first - and then, why build just one... you mention the distance/rotation speed issue with a centrafugal toroid/disc preventing expansion - I reckon you build it big enough in circumference you can onion up a few layers - outer layer might start to become noticible increase, but not opressive - but it's another excuse to be building more of them than one - you want expansion capacity.
