1. No, improvements make a multiplier to the total added for income per happiness level. If you have every income/happiness increasing improvement, you'd have a multiplier of 2.07. So to find the income increase per happiness point, you do the following operation: 1 (happiness) * 2.07 (improvements) * $2 (generic amount per happiness point)
2. I made a mistake on that one. Anyway, I'll show you with an example. Let's go with two of the income increasing improvements, bank and school. Each bank is a 7% increase upon income, each school is a 5% increase upon income. When you figure in two banks, you add 1.07 + 1.07. When you figure in a bank and a school, you multiply 1.07 * 1.05.