Have you done any true diagnostics on it or looked at a wiring diagram? If not you are kinda' just throwing parts at it and hoping you guess the right thing. It could be the clock spring causing the issue, and you could just happen to have got a used clock spring with the exact same issue....but maybe something else. Always nice to be able to test out the used parts but not always an option. You don't have to be one of those YouTube diagnostic guru's but there are a few things you can check.
- I would get a wiring diagram and see what the radio controls and horn share in common in the circuit. My guess is they go into the same connector at some point or share a common power feed. Also verify if the cruise control circuit uses a different connector or power feed. This will tell you where to look.
- Haven't really messed with a clock spring but would think there is some way to test it? Maybe check continuity on the connectors on both sides? That would tell you if there was a break in the circuit causes by the clock spring.
- At least do a closer visual look at the wiring and connectors in the steering wheel or column. Not saying to just yank on all the wires, but you should be able to apply a decent amount of pull on the wires going into the connectors without them ripping out.
I do almost all of my own work because I don't like having to pay a shop....but there is also a point in time where you have to think about whether paying the diagnostic fees of a decent shop is better than spending a bunch of money on parts. Not sure what you paid for the used clock spring, that didn't work, and now you are looking at paying $500 for a new clock spring that may or may not work. You can quickly get to the point where you are spending more money on random parts than just biting the bullet and paying the diagnosis fees from a shop........and if they guess wrong and replace the wrong parts, they are the ones that should eat the cost.