So far in rewatching the classic episodes, until March 1992, I don't think Darla was ever given an on-screen last name. So far Dinkle is just the credits name (though not in the US ones...) which is kinda surprising because Maria the maid was once (!) given a family name in an episode which never made it to the credits, though.
Any time, in summary he was a prototype for Bo Buchanan (rich son, learns to respect the family, and settle down due to the love of a good woman). So, once Bo move to Llandview there was no need for Tony to stick around.
I saw both L&F and FRFP when they were on. Clearly Amy was originally intended to be the bad girl (the Rachel or Erica Kane) trying to come between Austin and his true love, Laurie. However, Christine Jones and Rod Arrants had so much chemistry, and Christine was just so much more interesting than her counterpart, that there was a quick switch, and Austin and Amy were now the couple to root for.
Rod Arrants clearly had what it took to be a TV star, and Richard Backus was an excellent villain. Christine Jones had star quality, too. She was a great substitute for Erika Slezak briefly on OLTL and she played the evil Janice Frame on AW, Victoria Thompson having begun as the nicer Janice.
I was also a fan of David Abbott, the youngest brother Bentley Saxon, a short, funny, cute guy who didn't get a whole lot of story time. According to imdb, he is now known as Abbott Alexander, an actor and casting director.
I would propose that one of the flaws in the creation of Tony was that he was predestined to be with Pat so that they could re-play the AW chemistry. As a result, Tony lacked depth. He could have had more mysterious motives regarding the Lord fortune, creating more conflict for Vicky by wanting to gamble the fortune and go into riskier investments. I mean they didn't even play the beat of Vicky's disappointment that Victor was so pleased to have a son. He could have been an excellent partner in crime for Dorian (much like David was, years later), He was also into nightlife and fast cars, so he could have been more noncommittal and hard to settle down. Instead, the writing was on the wall for Pat and Tony to be together after a series of misfortunes, so it all seemed too predictable, and lacked spontaneity.
And yet, spoiler alert, Pat and Tony didn't wind up together after all..