Good tips. The only quibble I have is that "a severability clause" generally means splitting the contract up into pieces, not ending it. The proper term is "a termination clause".
The other thing to add is a "attorneys fees clause" so if you do have to sue you can collect your attorneys fees as well.
Do such clauses actually hold up in court? I've been told that generally in a civil claim each side is responsible for their own legal costs, regardless of who ends up "winning."
The other thing to add is a "attorneys fees clause" so if you do have to sue you can collect your attorneys fees as well.