Good points, Swordmaster.
I'm going to archive something here; a way to obtain even lower levels:
Go right corner:
Took me a while to find where I put the information, but I found it.
The reason you can get the levels a little lower is because Crinkles is incorrect in his reasoning that you should always use your highest-level character to absorb exp from a battle. The flaw in this is that characters out of party still absorbs 75% of exp, but only gain at most 1 level. So if you have 2 or more characters who are around the same levels, it might pay to distribute the exp more evenly amongst them.
In particular, note that Robo, Frog and Lucca have similar levels by the time you reached Medina Village, and in particular there are a whole stretch of battles where you can either choose to have Robo fight and absorb exp (and so Lucca, out of party, absorbs 75%), or have Lucca absorbs exp (and so Robo absorbs 75%). I wrote a program to check all combinations of Robo/Lucca usages and found a few combinations that are better than using Robo throughout.
In particular, I verified (thru playing) that this combination works:
-use Crono,Marle,Lucca with Heckran
-use Crono,Marle,Lucca with Deceasedx3 (2nd battle on Zenan bridge)
-use Crono,Marle,Lucca with Zombar
-use Crono,Marle,Lucca with the Reptites when you first go to 65000000 BC
Use Crono,Marle,Robo for the other battles just as Crinkles suggested.
This caused something good to happen: right before the battle with Magus, both Robo and Lucca are at level 14, with Robo having 120 exp to next, and Lucca 1270 to next.
In addition:
-use Crono,Frog,Robo for the Magus battle. This one is weird. First of all, don't level up Frog to 14 before this battle as you would have to do w/ Crinkle's method.
Here's the deal: proceed as usual until Magus enters his DarkMatter phase. Frog, being level 13, will not survive DarkMatter, but Robo can! So revive Robo just before Magus' first DarkMatter. From that point on, whittle out Magus' HP with Robo, healing as necessary.
But don't let Robo deal the final blow! Instead, when Magus' nearly defeated, after a DarkMatter immediately have Robo revive Frog and give Frog a barrier (you can get one in Magus' Castle), and restore Frog's HP to full. Then during Magus' next DarkMatter, Robo will be dead but Frog will barely survived, then quickly have Frog finish off Magus before the next DarkMatter.
I think you also need to make sure to give the SilverErng to Frog, and the Speed Belt/Dash Ring/whatever to Robo. Anyway, by doing it this way, Robo absorbs 0 exp, and although Marle absorbs exp, since she's out of party she only gained one level, to level 5. So you end up with the following levels:
Crono 1, Marle 5, Lucca,Frog,&Robo 14
Finally, for the battle with Nizbel II, use Crono/Marle/Ayla. It's very tedious and hard but possible, but be prepared to use like 80 midtonics and 30 revives (or something along that line). Have Ayla absorb the exp of course. After this battle and then the Azala battle (same strategy as in the FAQ), you end up with the final levels as I've stated.
You also have to purposely lose the battle with Golem, otherwise Lucca,Frog,Robo,and Ayla would all level up by 1.
Then you get the wallet and from that point on just follow the FAQ.