In the first movie, Drac said garlic makes his throat swell, but come Summer Vacation it shows that him eating garlic actually causes flatulence. Why is this? Because he lied! It's embarrassing, so he came up with a believable lie to cover the truth.
It was also garlic oil that caused the problem. For all we know, straight up garlic does make his throat swell.
Equally possible, if he had a bad reaction to it hundreds of years ago he's unlikely to have any again. It's common lore that as vampires age they become more powerful, and even in humans allergies can change overtime; perhaps what used to make his throat swell just gives him bad gas now.
As mentioned under Artistic License Linguistics, Transylvania's official language is Romanian, which belongs to the romance languages. So even if he had spoken in his native language to Ericka and not just Gibberish of Love, it still would have been appropriate.
The immortality issue from the previousmovies is also at play here: Dracula, as a vampire, will probably outlive his second wife again, and Ericka will be stuck seeing her husband remain exactly as he is while she grows old and dies.
Wayne and Wanda get tranquilized at one point, and Wanda, as always, is depicted as pregnant. Hopefully, the tranquilizer serum hasn't caused any harm to her unborn children.