A prenup is a very flexible instrument. A prenup can address financial agreements, and intimate agreements. It cannot do anything that adversely affects the right of a child to support. Some couples use a prenup to avoid creating any community property in the marital estate.
Yes, but there is a caveat. The agreement to waive retirement is documented in the prenup, but Federal law (ERISA) requires a ratification of that agreement after the couple is married. You sign the prenup prior to marriage, but you waive any rights to retirement after the marriage.
You can add language that penalizes him if he does not quit smoking. It could be a monetary penalty or another type, like no watching football games at home if he continues to smoke. You can be creative.
You can craft languages that requires sex on a regular basis. Again, there could be a penalty for non-compliance or a reward of a dollar amount of your separate property being gifted to the spouse for every year of compliance.
You should always have your own attorney to review and explain the terms of a prenup written for your signature. The prenup should not be so one-sided as to indicate that you had little or no bargaining power as to the terms of the prenup. There are many ways to make a prenup fairer. Gifts of separate property based on years married or upon the death of your spouse can alleviate your fear of being left with nothing.