You want to change to level 4 with Frieza? Currently there is only one transformation. And AMX is a program by which you can run scripts or plug-ins, it is pretty simple, you just have to find the site. There is one plug-in out there which you can control the starting power level though.
The bot idea is a lot better than setting everything up properly, I do it all the time when I want to mess around. Just create Ultimate Bots and turn all of their abilities to off and 0%
What do you mean it crashes at 400,000-500,000? That is very low for a powerlevel...