You are confused, so let me help you clear things up.
Amil and preterist are orthogonal to one another. The sets are (amil, postmil, premil,dispensational) and (preterist, historicist, futurist, idealist). One can be a preterist postmil or a preterist amil or even preterist premil. The only thing one cannot be is a preterist or historicist dispensationalist. (Dispensationalism require an association with futurism.)
Riddlebarger is a historicist amil who happens to interpret a portion of the Olivet Discourse as referring to AD70. This is not uncommon, but it does not make him a preterist. In fact there are many dispensationalists who also happen to interpret portions of the Olivet Discourse as referring to AD70. (They usually are the ones who push for a “double fulfillment”, AD70 and the future “great tribulation”).
I hope this explanation will help you to carry on a reasonable discussion on the subject in the future.
So then he is what: an Amillenial Historicist with Preterist Leanings. Where do you fit in that classification???