Based on your description and fantastic LSAT score, I think you will do very well on the GMAT (there is still a chance to screw it up but I think we can check mark it for the sake of discussion). Ross is a great and very competitive program; it may be tough to get in with just a few years of legal clerk experience but not impossible.
One weakness of a dual degree I can see is that your lack of work experience (not for admission sake but for your sake of looking for a job). It is tough finding a job (even with a Ross MBA) if you have not proven yourself in the business world - one reason it is not recommended to get an MBA without a few years of work experience. Your main chance to get the experience and exposure to employers is the internship in the summer and I am not sure how it will work with JD/MBA schedule. MBA is a good thing to have on your resume but due to lack of experience, you will have to start a bit lower on the ladder and work your way up. You have to pay your dues and you do that before or after (most of the time, not always)
The only negative I can see with dual degrees is that they are somewhat of a weaker proposition than just a dedicated degree (usually you don't get in as deep and with the interruption in the LAW school, you have to catch up after the break for bschool). The U of Michigan JD/MBA program is actually the better of what I have seen. You would get 3 semesters in business school and 5 semesters in Law School. So, you are technically only skipping a semester of BSchool and a semester of Law School.
You will also get out of sync with the friends you make in law school since you will go to bschool the second year. On other hand, in bschool you will be a bit out of sync since everyone will be doing internships and looking for jobs whereas you will have another 2.5 years to go until you complete the degree and can be employable or take the bar.
I think the bottom line is - you will do great with a LAW or JD/MBA or MBA degree from Ross or any of the schools you have mentioned - there is no doubt about that. So, the worst case scenario is you spend a year or two extra at school and have an extra $75K in student loans.
My suggestion would be - think of jobs you would like to have and do and then research what experience/background/education some of the key people in that field have. If not, and the extra $70K and 1-2 years does not scare you (and you feel confident you are capable of interviewing well and getting a job locked in), then in the grand scheme of things and in retrospect - $70K is not that much.
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