is there an article here how to calculate retirement funding needed 30 years from now? is it my current budget less tuition?... how on earth am I supposed to estimate what grocery will cost me then?

You calculate it based on the current price of items you might need in retirement. So you can get rid of tuition and maybe a mortgage, but may need to include added healthcare costs.

I assume that clothing, household help, utilities etc all stay the same (of course except for overall inflation) and just remove tuition and mortgage? is that roughly the thing?

Depending on support for married children. If you do support that would be an expense that might come up, if you don't then Clothing, Groceries, etc can go way down. Actually marrying children off might still be an expense, but will go away eventually.