re: The only way to fix Congress is through a convention of the states.

The constitution needs:
1. A one object rule/germaneness rule for legislation
2. Some guidelines for budgeting (balanced budget shouldn’t always be the requirement, but usually).
3. Defined powers and limitations for what Congress can/cannot grant to administrative agencies
4. Some cleaning up and defining of the “necessary and proper”, “waters of the united states”, “navigable waters”, and “interstate commerce” clauses
5. Some precise language regarding the 2nd amendment, such as “the right of all citizens to keep and bare arms shall not be infringed”

There’s a lot of other things which could certainly be arguable or addressable, but these are the most important, imo. These could massively and fundamentally change the balance of federal power.