1. Ignore whatever your broker says you can "afford" -- I swear, those guys must be required to get specialized training in alternative math or something. Their advice is fundamentally incompatible with FIRE.
2. Personally, I have always been most comfortable when we were at @1.5x or less, because then we wouldn't lose the house if one of us lost our job, and I am much happier now at well under 1x. But my personal experience (of the "oh shit" variety with unexpected job losses) probably means that my personal comfort level does not reflect the norm.*
3. Ratios are meaningless in general, and even moreso for someone looking to FIRE. Your desired FIRE date and the 'stache you need are so completely personal that what works for someone else likely has no bearing on your life and could even be misleading.
4. The only way to get a good number is to do sample budgets. Start with your new income, including any adjustments to account for differences in gross income, taxes, benefits, etc. Then subtract out savings -- #1 is the savings necessary to reach your target FIRE date, but don't forget other things like a vehicle replacement fund, saving for college, etc. Then look at your current non-housing living expenses, including things like hobbies and vacations and such, and try to adapt them for your new surroundings (e.g., difference in grocery costs, commute costs to your target area, local restaurants and events and such you might want to go to, and the like); subtract all of that out. What you can afford is what is left.
If that number is too small to afford reasonable housing in your new area -- and, yeah, it will be -- then you need to go back through the budget and figure out what gives. How you answer that question doesn't matter as much as asking it in the first place. Where people go wrong is in buying a house without doing the math (or worse, relying on self-justifying math, a/k/a "well, I love the house SO much that I'll be happy never going out"); that approach inevitably results in locking themselves into an expensive house (which also comes with more expensive carrying costs that they also failed to consider), not actually changing their lifestyle past the first couple of months (because why live in such an awesome place if you can't take advantage of it! -- a/k/a more rationalization to do what they want), and now it's two years down the road and they wonder why they can't seem to save anything. In the real world, the money has to come from somewhere. Do the math first, and then at least you are making an informed decision and can knowingly accept whatever the tradeoffs are that come with that choice.
*Think Scarlett O'Hara, except with "by God, I will never have to sell up and leave my entire life behind and move across the country again."