Are you typing on a smart phone? There are a lot spelling errors that makes reading some of the stuff you wrote hard to follow.
In your post
#25,
I wasn't sure if you meant you renamed the present *.firm [from your main setup] to
boot.firm. This is being mentioned to double check you're closely following the directions without deviations.
Your 3DS should have launched SafeB9SInstaller with that FIRM payload named as
boot.firm like
this.
***
If your 3DS still hangs at black screens, it seems the motherboard is not able to properly communicate with the SD card.
1. Check if the SD card write protection switch is not set to the LOCK position.
Picture #1.
2. Clean the golden contacts of the SD card.
Picture #2.
3. See if the SD card slot reader has dust inside. Clean it with compressed air or vacuum cleaner.
Picture #3.
4. Try reinserting the SD card at several different angles to get better connection.