It sounds like you have done some reading, but here is a site with plenty of documents, as well as some diagrams that could give you some idea's on which way to go.
http://www.solidsignal.tv/dishpro_installation.asp
Two things to consider; (1) are you looking to be able to install a satellite receiver in each room, or (2) you would like to be able to receive the satellite receiver's output(s) in each room?
That will make a difference in how you will attempt to configure everything. The RG59 is not recommended for satellite signals between the dish and satellite receiver using either DishPro or DishPro Plus technology. This technology sends the Left Polarized and Right Polarized signals down a single line at the same time, as well as sends the signal requirements for both tuners of a dual tuner receiver at the same time.
Using diplexers, you could normally backfeed the modulated signal from the 522 with the satellite signal, however, I don't know if it will interfere or not when using RG59 instead of RG6. But you should be able to send the modulated output across the rest of your RG59 distribution system.
You could combine the 522's modulated output with an OTA TV signal, however, it would have to be on a channel not being used.
Likewise, combining
TV Equipment Output,
OTA Signals, and
Cable Signals, can not be sent across the same line unless each were on a different frequency (Channels). This could be accomplished by buying a modulator for each channel you needed to convert to another un-assigned frequency. However, then you will have to start balancing outputs so that one did not interfere with the other. Ex: Channel 5 from a piece of local equipment could wipe out Channel 6 OTA.
Cable Internet -- Your cable modem will work best without splitters, or maybe one splitter. Your cable modem could then feed a wireless router, or maybe a wired router that could make use of your home wiring, to provide internet service to other computers.