[MrObvious]

Try flashing a stock ROM, hard reset and wipe out the Internal Storage too (back up everything!). Then move to something like MightyROM 4.8 or whatever. I love MightyROM and it runs very stable for me. If you get a good running ROM with very few or not any bugs then things will be smooth for you. After that you should be good to go, otherwise you will have to reflash stock, relock, and get a new phone.