I understand the 30 knots for yourself and students with you in the plane. 15 x-wind is getting up there for sure, especially if you're teaching and not doing the flying yourself. But "0" for a first solo, you'd be waiting forever in michigan for that. My first solo sign off was on a day of 7 knots and it wasn't right down the pipe. It all depends on the student and the proficiency.

On that note if the club has limits that's what you've got to go on. I can say my personal limits are about 30 knots total also or somewhere in that area. I had to land at an airport with only two parallel runways with a direct x-wind of 18G27 in a 172 and it wasn't my best landing but it wasn't bad either. I wouldn't PLAN on doing that again. It was outside the poh's recommended max x wind.

You're best bet is to know your own limits, and only test those limits in increments or with an experienced instructor to build confidence