Okay I'll do the best of my ability to answer, even though I didn't have a lot to do with it:
1: Regarding 3.5, it is compatible, mostly because they were scheduled for January/Feburary release but they got pushed back when 3.5 was first announced.
2: PC is correct. He wrote the chapter on Sorcerers (I remember him telling me and a few others that). If it says otherwise, that's a mistake. Mike Gill did Bards. Ethan Skemp was the one doing wizards. (Which in it self is interesting but I'll let him handle that.)
3: Compared to tome and blood, the sorcerer has a lot more going for him. While those of you that have Relics and Rituals 2 will understand this, I think it bears repeating. Sorcerers in the Scarred lands have special bloodline, not all of them draconic. Some are titanic. Thus they have what are called Scion feat. Scion feats allow sorcerers to cast certain spells +1 effective caster level. Plus a bonus on various skills/abilities/etc. In exchange for this, each time a new known spell slot becomes available, that must be filled by one of the sorcerer's scion spells. (There are two for each level) These must be filled as required by the feat. Also there are two or three sorcerer only Prestige Classes. Two of them are Scion feat related, Blessed of Mesos, and Angel-blooded.
Hope that's helpful.