There is a dogma: priests of the Catholic Church confect the Sacrament of the Eucharist and it is the True Body and Blood of Christ Himself
There is a fact as certain as the dogma: My priest confects the Sacrament of the Eucharist and it is the True Body and Blood of Christ Himself

The second is not dogma, but it is as certain as dogma.

What?  This has nothing to do with SVism.

Second proposition is only morally certain, not dogmatically.  Could be that your priest isn't valid for one reason or another.

Yes, but absolute moral certitude. For practical purposes of faith, because we offer adoration to what looks like bread but we know is not (hypothetical notwithstanding).

We also know that the men commonly claiming to be true popes cannot be so, because the Church could not violate Mortalium Animos to the universal Church in all Her organs of the magisterium.

What is the definition of "absolute moral certitude"?

"Our certainty regarding the validity of a sacrament in a particular case is not, to be sure, that of evidence [i.e., metaphysical or physical certitude], but neither is it merely moral [certitude]; it is truly and properly the certitude of divine faith."
     - Billot

It's not dogma itself, but it is a dogmatic fact.

“A dogmatic fact is a merely historical fact, which however is so connected with revealed doctrine that its determination is necessary for the complete guarding of the deposit of faith.”
-  Sacrae Theologiae Summa by the Jesuit Fathers of Spain (1940's to 1950's)

This is why saying "Leo is not a true pope" is a dogmatic fact, not a dogma.