You are not being ridiculous, you are the voice of reason! You should draw them that famous graph that exhibits the SPF value as asymptotic from number 45 onwards! A picture might be worth a thousand words here. Also, regardless of chemical sensititvity issues, do you think it is possible for a human test panel to validate that SPF value? Might be nigh impossible, and certainly VERY expensive. Good luck.
Totally possible! Specially if the product isn’t for the US market. I’m seeing even SPF 130 sunscreens. But you’ll need high performance filters, like Tinosorb M and S, Uvinul A Plus, Uvinul T 150 etc. Basf sells a lot wonderful UV filters. A W/Si emulsion also boosts the SPF a lot!
With 8% of TiO2, 7% of OMC, 2% TNSB-M, 3% of TNSB-S and 2% of Uvinul-A Plus in a W/Si emulsion you will achieve something near SPF 100. Less (maybe 60) if your emulsion is a traditional O/W emulsion.
Too much filters? I don’t think so. 22%, 8% being inorganic… In the US many sunscreens have much more UV filters and offer low SPF’s, since there are just a few (and not so good) filters approved there…