If your living room opens up to the dining room and kitchen, the sub isn't going to have the same response as it would in a 14x14 room with four complete walls. I don't think the subs you've chosen will be overkill at all. To avoid disturbing the neighbors, be sure to use the spikes to minimize the coupling of your sub with the floor. It won't be an absolute solution, but I think it'll help.
I think you'd be happy with either choice for your sub. Since you don't have bass management, you might consider getting the cheaper of the two subs, then using what's left of your budget to roll your own bass management. A MiniDSP, 2-way advanced plug-in, and UMIK-1 for around $200 would do nicely if you don't mind a bit of reading, asking questions, and figuring out how to use REW. I have one and I love it! Or maybe you'd prefer a little pricier DSpeaker Anti-Mode box of some sort from SimpliFi Audio if you'd rather have something more automated and less fiddly (although customer reviews of the Anti-Mode gadgets seem to be quite hit-or-miss). But if the shiny features of the flagship Anti-Mode 2.0 Dual Core start to tempt you, remind yourself that you can probably get a more capable Marantz SR7008 with Sub EQ HT for less money.
To answer your questions directly:
1. No, they aren't too much for your room.
2. PB2000 is ported. It's the SB2000 that's sealed. You'd be happy with either of your choices I'm sure.
3. Sealed vs. Ported is not nearly as relevant as well-tuned, standing on its own merit vs. existing to sell the rest of a complete 5.1 speaker package. Many well-known speaker makers make subs to sell more of their other speakers. Since SVS and Rythmik have their roots in subs, this isn't really a concern. They're both well-designed and ought to handle music very well, assuming you take the time to do the subwoofer crawl and minimize unpleasant room interactions.
4. I'd start at 80 and salt to taste.