You have made your case that complying to seemingly subjective political laws (arbitrary yet inflexible standards for "inebriation", and arbitrary yet under the code-enforcement agent's discrection "speed limit") is a matter of following a contract. You have not made your case that the seat-belt laws are not part of that contract, but are something that benefits the insurance company. By the mere fact that code-enforcement agents and the judges are collecting taxes fines for seatbelt violations should seem to even the layman that seatbelt laws are a part of that driving contract and privledge.
Your claim that driving drunk is "fraud" doesn't meet the legal definition of fraud any more than any legal form of impaired driving is "fraud". So either you need to show how "driving drunk" is indeed fraud, or drop that unsubstantiated claim.
It seems that your primary reason for liking "drunk driving laws" but not liking "seatbelt laws" is that the former is common sense and the latter is just "stupid". This is a fine example of why Libertarianism is just warm-up act for Totalitarianism, for you declare by fiat that one is common sense (even though the declining acceptable levels of intoxication bear little correlation to actual impairment) and the other is "stupid" (just because you may not like buckling up, or that is some aspect of the contract that is too inconvenient and too burdensome).
My primary transportation is a motorcycle so seatbelts are when I cage-up for events where being exposed to the elements is a bad thing. Not only does this Cat 'N Mouse game of life make wearing seatbelts necessary so as not to take penalty points from "The Man", but there hasn't been a single "drunk driving" law that has kept drunk drivers off the road. It is in my interest, my family's interest, my friend's interest, the premium payer of insurance's interest, the emergency crew's interest, my client's interest, and the interests of all of those on welfare that depend on me to work, that I survive a motorvehicle trip across town. That is why I wear seatbelts.
You may call seatbelt laws stupid, and I hate the fact that people are so damned irresponsible, and busy-bodies are so power-mad that the government feels a need to lay down these draconian responses, but as much as you feel that the potential harm that a drunk driver can do merits Gestapo like check-points (where they also check administrative violations like registration, inspection, valid permits, and fish for other violations such as guns, drugs, open containers, contraband, illegal aliens, etc.) I can come up with equally valid reasons to why compulsory seatbelt laws are just as safe and should be part of every driver's legal responsibility.
But you might still just call it "stupid" because seatbelt laws have their roots in the insurance company, whereas head-on collisions caused by drunks must not effect the insurance industry.
While I personally think that seatbelt laws are "stupid" and that drunk driving limits are "arbitrary and do not necessarily corollate to impairment", I think that citizens of a State (not the Federal govt, which has mandated the BAC %'s) have the right to set restrictions on seatbelt useage and BAC %'s. While the primary immediate beneficiary, besides yourself and family, for the seatbelt laws are insurance company, I agree that States have a right to make this part of the contract for driving privilage.
Drunk driving is "stupid", "dangerous", "harmful", and violates the contract that you make with the State in which you are driving (I don't think any state allows you to drive drunk). It may not fit the legal definition of fraud, however I think most folks would agree that using the roads "fraudulently", i.e. outside the terms of your contract, is a lose useage of "fraud". You're splitting hairs.
You have made up mind about libertarianism, so I will not bother confusing you with the facts. To say that libertarianism is a precursor for totalitarianism shows just how uninformed you are on the subject. No matter.
Regardless, I do NOT approve of roadblocks to check for DUI, seatbelts, firearms, valid registration...
But if the public gets together and creates a community ....all of a sudden the "initiate force or fraud" mantra is heard.