You need to set Booking duration to “Custom” and Custom Booking Duration to “7”. You can also set Weekly if it works as you need.
Then you set Minimum Booking Duration to “2”, so it forces clients to select at least 14 days.
Concerning the price, you can set the product price to $75 (so 2 weeks cost $150) and add a $40 discount from 3 weeks (so each additional week costs $35). Don’t forget to set Duration Discounts in “Cumulative” mode.