Thank you all for the further information. The foam guy mentioned needing an air exchanger, and when I asked he said they cost around $1000 and are not hard to install, so that sounds doable.
It is partly a labor of love and partly of necessity, since I have been planning to leave here this summer and time is running out. The house is tall and narrow and awkward, so I look just like the sort of person who should live in it.
The house was listed as having been built in 1920 by the county records in the tax auction, and it has to be close because there was nothing in the area till 1893 when the paper mill was built, and the house was built before it closed in 1933. The green foam sounds good, and I noticed today that the foam for the basement walls is listed a $1.80/bf rather than $1.40 like everything else, so maybe that's why. I don't mind hanging drywall in the attic if needed, it's cheap enough and not that much work. Thanks for the tip on sealing penetrations, I'll bear it in mind. I asked if I should be putting in wooden fireblocks at the second floor level, and that's when he said he would do it with the foam.
That's odd that CA doesn't require the higher insulation value. It's good to know that rockwool won't burn. He said that was what code required around a metal chimney installation for 2" before the foam begins.