turn signal flash really slow ...

Let's be sure you are seeing the lights you think you are.

The brake lights should be bright.
The parking / running lights should be dimmer.

The turn signal and e flashers interrupt the brake lights to make the flashing so your turn signal lights should be bright not dim.

As for attaching a ground wire to the bulb socket and the turn signal stops flashing but the bulb becomes brighter says to me you have a bad ground there at a minimum.

There are other grounds that need to be attached for the turn signals to work properly. The front light harness is one of them.

I had my grill off and then noticed my turn signals would not flash the rear bulb would light but not flash.

Just some thing to investigate.


And yes a bad turn signal switch or bad connector can have all kinds of issues.