Having problems with my car PLEASE help?

[Dave]

OK I have a 1997 Thunderbird 3.8L and I was having trouble with my H/O alternator so I had it redone and I had it done with an external regulator so I can control the voltage output the dial goes from around 12.4-15.8 volts and I got it all hooked up and I had it tested and @ 2000 RPM and it only averaged around 59 amps and I no I should have got alot more than that. Also once I got the alt hooked up I started getting an air bag code of 42 and it just flashes 4x's then 2x's and dunno how to fix it. Another thing is that my headlites don't work either and there not gettin power and can't find the fuse does anyone know where it is so I can check the fuse? I have an optima yellow top under the hood and a kinetik 2400 in the trunk and when I got my car mic'd (140.6 and air was comin outta the trunk so I lost a db or so) oh and this was on my other alt my voltage was dropping below 11. How do I fix that and I had it up to 2000 RPM to get a little more power. OK now here is my setup I have a custom fiberglass box with 3 DB Drive 12's (Model # PLW12D4) and a Sundown SAZ3000 and I have Oxygen speakers inside 2 6 1/2's (Model# OM6-90) and 2 6x9's (Model# OM69-200) hooked up to a Sundown SAZ 100.4. So can someone please lemme no what you think I should do to help with the voltage dropping do I need more batteries or better alt I no this one needs replaced. Oh and I dunno if this makes a differnce but everything is wired pos to pos n neg to neg and I did the big 3 under the hood. If you need anymore info let me know and I will get it to you. I really appreciate any suggestions and please explain in laymen's terms cuz there are some things I don't understand like when it comes to ohms n volts and things like that. So thank you for your help.