If it helps on, our recent trip to San Fran we had very similar temperature range. I also run hot. It drove me nuts because the temperature would fluctuate so much during the day, and I was constantly peeling off or putting on layers.
Based on that experience alone, I'd definitely suggest packing extra scarves, especially warmer ones (lightweight pashmina in generous size). Scarves always make a huge difference for me, not just fashionably speaking.
I'd also suggest packing a lightweight non-bulky cashmere long sleeve sweater if you have one? I brought my Vince Ombre cashmere sweater, which I is so light, I can roll it up into my handbag and it takes up very little room. I carried it with me everywhere, and popped it over pretty much everything - dresses jeans slacks - whenever I needed the extra warmth, because day started out hot & short sleeve/sandal weather but wound up windy and chilly.
Does your hubby have a backpack? Mine brought his to Paris and it came in handy -- we'd load it up with blanket, wine glasses, buy cheese, wine, baguette and go have picnic in the park. Of course I also offloaded extra shoes to him to carry!
I get you on the sandals and foot issues, totally. But one thing to be aware of is that there can be fleas on the subway in Paris. Learned the hard way that there is a reason Parisians wear long pants, socks, and covered shoes in the subway.... even in August and 90 degree temps...
