Not enough gain on the amp?

I have a SAZ-3500D (not the newer one) and I tried to set the gain with a multimeter, but all I can do is max out the gain / bass / bass remote and put my head unit on 20 out of 35 (cause that's where the normal speakers start to sound like crap). Also I'm running (2) dual 2 ohm 12' HCCA's wired to 1 ohm and I don't remember the specific head unit, but it was about $250 made by Kenwood. So according to Ohm's Law, I should need need about 59 AC Volts, but with everything maxed out like I said before, I can only get it up to about 45 volts... I've had it totally maxed out for the passed couple of days, and I the subs seem totally fine, but will running the amp at max be ok for its health? And also is there some way that I can increase the gain a little more so I can reach my full potential?
Thanks in advance, and my system is finally operational so I might through up a build soon (Mazda 6 s)

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FML, I'm a *******... Not only is this my first big setup, but it's also my first ever multi-sub setup as well... I wired it parallel, so .5 ohms then; I guess it's a good thing that I have a good amp. And as far as the electrical goes, I have 2 XS Power D5100s in the back, a D1200 under the hood, Cadence 0 (power) and 8 (speaker) gauge wire, 2 positive runs to the back (currently only 1 hooked up because I'm waiting for some hobo on amazon to ship some more fuse holders), and I just got my Excessive Amperage 225 amp alternator in the mail this morning so hopefully I'll have that hooked up before the end of the week, along with the other 2 thirds of the big three.
Currently with the 3 batteries, a stock alternator, and one run of 0 gauge to the back, it will drop to the 11's with the volume at 20 (which I've only done once). For normal listening it stays above 13 (or 12 if my friend is controlling the bass remote lol)

Now that you guys have cleared up my stupidity... Should I leave it wired to .5 ohms? I bought the amp used, but I opened up the back just to take a peak, and it looks totally pristine and shiny. Also, my gain issue still has the same problem... yes I maxed out all of the head unit's bass / sub settings already, and lets just say that at .5 ohms the amp produces 4000 watts (just an example, please don't argue over sundown potential or box rise), that means that I'm still underneath the full voltage (which is about 50v) with the gain maxed out. So what should I do about that?

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Ok thanks. But when you say "something to set gains the right way" do you mean one of the SMD DD-1's? Doesn't tuning it with a multimeter and then bringing it down a couple notches to give room for distortion do the same thing?

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