Can you elaborate on the details or circumstances these parts outlined? Particularly in regard to provisions or protocols to be followed in the event you become unable to render product service (due to disaster against the product or its infrastructure, personal circumstances, or otherwise).
I'm in a similar position that you've described. I'm mostly a one-man shop with a SAAS product that has a Fortune 100 customer. As it becomes increasingly integrated within their company they've voiced concern over what happens if I become unable to render service. We likely have contract amendments coming for code escrow, but I've no experience in this particular area, so thought I'd ask what you learned from these parts of your contract.
If it matters, the product is tightly customized to the customer's work flow, and provides a solution they've been unable to readily find elsewhere. So in the event that service can no longer be rendered, having them subscribe to another product wouldn't be immediately viable.