This is not a criminal defense question; It is an administrative / regulatory / licensing question, and I cannot tell you whether or not you have to report your dismissed WY DUI after a deferred sentence and probation.
If you want to increase your odds at getting a competent answer then you should ask the only folks who can provide you an answer, to wit: the FAA. For your convenience I have attached a link to their website below.
Please see: https://www.faa.gov/licenses_certificates/medical_certification/
What I can say is that unfortunately, it is probably a safe bet to assume that if you were arrested anytime in the digital age then your criminal record will almost certainly remain with you forever. To some degree or another this is true regardless of whether your ultimately seal or expunge a case. All arrests are matters of public record, and, even if they are subsequently removed from the public record they still remain alive and well in various private records. This is one down-side to technology.
You might want to do your own background check to see what pops up. Forewarned is forearmed. If your prior indiscretion appears then, for better or for worse, you are probably best advised to take the wind out of the sails by admitting your past issues / indiscretions to your present (or potential) employer, lender, landlord, licensing authority, admissions committee, etcetera, rather than waiting for them to find out on their own, but that's a personal, not a legal, decision.
Wishing you luck and hoping that I have been helpful in properly re-directing your question.