Q: Where are you getting that you have to have 34 or more applications on the same subject?
A: The same reason that we assume that when it says 2/3 of both Houses of Congress have to propose an amendment on the same subject before they can send it out. It wouldn’t make much sense if part of Congress proposed one amendment, part of Congress proposed another amendment, and part proposed another, and then they sent it all out to be ratified. The same holds true for an Article V convention for the purpose of proposing Amendments.
Q: How can you be sure that the states can control the delegates?
A: States had that power under the Articles and, thanks to the 10th Amendment, it’s certainly protected under the US Constitution too. I might add that nobody fears that the electors to the Electoral College might run away. They are appointed by the states but there is nothing in the Constitution specifically mandating that they HAVE to vote the same way as their states. Nonetheless, many states have passed laws making their electors have to vote the same way as their state, and it hasn’t been challenged in court. Furthermore, in more than 200 years, the most rogue electors we have had was in 2016, when 5 electors voted against their state. They certainly weren’t enough to turn the whole election. So if we can trust our states to make sure that we don’t get rogue electors, then we should be able to trust them to appoint delegates to an Article V convention and control them if they get out of hand.
Q: How do we ensure that bad amendments don’t get ratified? I mean, we ended up having the 16th and 17th Amendments ratified?
A: It’s true that we did get 3/4 of the states to ratify those amendments, but they were proposed through the proper channels. Meanwhile, the bad Equal Rights Amendment was halted in the state legislatures and when Congress illegally tried to extend the ratification period beyond what they had earlier put, they were slapped down by the Supreme Court. Thus, we can almost certainly stop any bad amendment. The risk of getting a bad amendment out of our convention is far far lower than federal courts, etc, altering out Constitution into something very opposed to what it was meant to be.