Recently bought a house with a suspicious electrical setup running to a detached garage. Garage is about 70 feet from the main panel. Feeding the garage is 10/3 Romex with no ground wire on a 30amp breaker. The romex is fed to the garage from the roof of the house overhead. Inside the junction box in the garage is a mess - 10 gauge pigtailed with 10,12 and 14 garage wire feeding several outlets, lights and switches (see second picture).
Would love some advice on whether or not this is a safe enough setup. We have no need for 30amp power so I’m wondering if I can just change the breaker from 30a to 20a.
Also, concerned that there is no ground wire and how to remedy without installing a sub panel.
Thank in advance for any advice!