Bitcoin to Stacks Value Ratio

Is there a price when Stacks is not worth it to mine because the price of Bitcoin is too high and the block reward for stacks is just not worth it? How does the system adjust for those types of scenarios? Do people just stop mining? How are those scenarios accounted for?

Unclaimed STX coinbases accumulate, and get awarded to the next Stacks miner who successfully builds a block. For example, if there are 5 Bitcoin blocks in a row in which no one mines, and then someone mines in the 6th block, then they get 6x the coinbase. Eventually, it will be profitable to mine if the price of STX is greater than 0.

Nice - is there a place to read the rules behind all the thought that went into designing they system?

I’m not sure this particular point is described in the SIPs, but in general, the SIPs describe the design of the system.