[Q] Phone refuses to boot with a rom topic

Hi, I've been trying to install a custom rom (at this point ANY custom rom) on my friend's phone. I have worked on several phones before, including my own sprint GS3, but this is my first time trying to work around a locked bootloader, and BOY is it a pain, haha. I'm no dev, but I would like to think that I'm pretty competent.

First a few things to note, are that the phone is currently on NI1 (Been too much of a sissy to go to NJ4 in case it screws something up, I don't even know why), it is the 16Gb version, I am using an external sd card to flash everything, and yes I am flashing loki-doki after everything.

So what I've done so far is:
- Try to install TWRP
- Find out that won't work and finally figure out I need safestrap
- Successfully install safestrap after using towelroot by ODIN-ing the NC1 kernel then going back to the NI1 kernel
- Try to flash Resurrection Remix and KToonsez kernel using a new rom-slot, and wind up soft-bricking (stuck on bootloader screen, can get to download mode)
- ODIN NB1 tar then ODIN NI1 update
- Repeat the last few steps several times because I'm too idiotic to realize that it JUST ISN'T GOING TO WORK!
- Finally find a reference to flashing the ATT kernel modules after the rom. That got me past the soft brick and safestrap screen, but I don't even see a boot animation

As of right now my sequence to successfully not soft-bricking (what an accomplishment) is to flash the rom>gapps>ATT kernel module>supersu>loki-doki>wipe dalvik/cache

Now, is it worth it having already spend a good 7 hours, just to get a custom rom? Of course not, it's not my phone and my friend isn't picky. He'd be just fine with rooted TW. However, It kills me that I don't know what's going on, so here I am lol.

TL;DR: Phone has safestrap, is rooted, but any time I flash a rom it gets past the boot loader/safestrap screen and never shows a boot animation, or anything past that. Can anyone help figure out what's going on please?

Thanks in advance.