The marriage to the heathen Ukie is a valid, non-sacramental marriage. Were the Ukie subsequently baptised, the marriage would become sacramental.
Non-sacramental marriages can be dissolved in favour of the Faith (Petrine Privilege, Pauline Privilege), but sacramental marriages can only dissolved by the death of one or both spouses.

Understanding marriage validity can be complicated and confusing to those untrained in canon law, whether Corpus or 17 Code or 83 Code. For example, the marriage between two baptised Protestants would be presumed valid and invalidity would need to be proved. Or,  Catholics are bound to canonical form for validity. Or, certain defects can be sanated (cleansed) at the root validating a marriage ex post facto. Or, a civil  marriage or one attempted before a non-Catholic minister can be validated by convalidation before a Catholic minister with delegation. Ah ... delegation! For validity, one must contract marriage before a priest or deacon with faculties from the ordinary bishop or with delegation from a parish pastor. Oh ... oh ... and Eastern Catholics must have their marriages conferred by a priest, never a deacon which would likely invalidate the marrige because, whereas in the Latin Church, the spouses marry each other before ecclesiastical witness, in the Eastern Churches the priest (and never a deacon) confers the sacrament on the couple.

A Catholic, even if fallen away, can never marry in a non-Catholic ceremony.  Ever.  There's no such thing as valid non-sacrament.  There is natural/putative marriage which exists between pagans, Jews, etc.

The OP is still married to his 2nd wife UNLESS there is evidence that the first union (his or hers) was valid and rendered the second union invalid.

I'm guessing he wants to prove his 2nd marriage was invalid so that he can contract a 3rd marriage.  

They won't go the Novus Ordo mass but they want Novus Ordo annulments.....weird.

Thanks Gray.  Lots of silly assumptions…

In the future I’ll leave out unnecessary context - it piques interest and engagement but sure does muddy the waters (tho many of the responses have also been intelligent and thought-provoking if not quite getting to the heart of my particular matter)

If anyone is still interested, here is what I consider the critical issue:

IS A NOVUS ORDER MARRIAGE TRIBUNAL A COMPETENT/AUTHORITATIVE BODY ???

Thanks Gray.  Lots of silly assumptions…

In the future I’ll leave out unnecessary context - it piques interest and engagement but sure does muddy the waters (tho many of the responses have also been intelligent and thought-provoking if not quite getting to the heart of my particular matter)

If anyone is still interested, here is what I consider the critical issue:

IS A NOVUS ORDER MARRIAGE TRIBUNAL A COMPETENT/AUTHORITATIVE BODY ???

You are asking the wrong question.  You don’t need a marriage tribunal (no matter if traditional or novus ordo) to answer the question of “Is marriage 1 valid?”.  No, it’s not.  Marriage 1 isn’t a sacramental marriage, which is the entire reason why the Pauline privilege exists.  Your questions around marriage 1 can simply be answered by anyone who has a basic knowledge of canon law.  The tribunal was correct.  But it doesnt take a tribunal to answer the question.  

  The Pauline privilege rules have been around since, well, St Paul.  So 2,000 yrs.  Your situation isn’t that unique or special.  I personally know multiple similar circuмstances.  Ask any Trad priest and you’ll get the same answer. 

I get the Pauline rules, etc have been around since forever. I’m not disputing that.  WHO gets to enforce those rules is the question

Plenty of Trad priests use the Pauline privilege and marry a person that was previously “married” to a non-catholic.  A tribunal isn’t necessary.