Personal modem, Comcast Business internet, and X1?

My employeer has an agreement with Comcast Business to offer a discount for their teleworker plans, and I originally purchased Comcast service through that plan. Along with this plan, I had my own personal modem – a SURFBoard 6141 – rather than a Comcast issued modem.  Once the X1 service was announced, I signed up for Xfinity, understanding that a Double Play plan with TV and phone would qualify me for the X1 platform; I could continue using Comcast Business internet.

After the installation, however, it seems all of my services including internet are offered through Xfinity and my Comcast Business internet plan is unused. (Even though I'm still paying for Comcast Business internet!)

Thus, my questions:

1) Can I use Comcast Business for internet, and still get X1 through the TV + Phone Double Play package?

2) If I can use Comcast Business for internet, can I then replace my Comcast modem with my SB6141 and stop paying $10/mo to rent a modem? I realize my modem won't support the cable phone service… that's fine, I'm only paying for it to get X1. I haven't used a land line at home in a decade.

3) If I do use my own modem and have Comcast Business internet rather than Xfinity internet, can I still use the in-home live TV streaming over xtv.comcast.net and the X1 iOS apps? Live TV streaming is the biggest reason I want X1, so I don't want to give up that feature.