"I have a sneeky suspicion the perps were freinds of his."
Either that or he thought you were the perp. In most places you only get to draw your weapon if there is a threat to life. It sounds like you or your brother were not able to make it clear to the officer that you felt your brothers life was in danger. You better do a better job in court getting people to believe you, or those charges will stick.
The charges of terroristic threats are probably for pulling & pointing the weapon.
Public endangerment would be that others in the public could have been hurt.
Disorderly conduct would be for causing trouble in the city/ county. This type of charge is usually used when people are doing lots of yelling, fighting or just being stupid in public.
That the finance company will not back you on any of this only makes things worse for you.
There are only 4 people who know what really happened, and the rest of us weren't there. It sounds to me like you didn't do a very good job of explaining what happened to the cop, either that or he didn't lsiten.
I just got off my watch after dealing with stabbing(s), DV(s), burglary(s) and loads of other garbage. I wouldn't have made the same call this cop did with you, but I am only gettting one side of what happened. Good luck.
PS- If he had been on the force for a week and a half, he would be in the academy. If he had been on the street for a week and a half, he would be working with his field training officer, who would be making all the calls.