The table doesn't go any larger
Your maximum legal damage is either 12d8 or 16d6 depending on whether you start even or odd (i.e. d6s or d8s, respectively), which would depend on your monk level in this case, and would be highest at 10th level before dropping back down to the 12d8 level, if you changed the build so it actually hit the end of the chart.
That said, your damage does still go up after this, there's just no rules or advice on how to do that. There's no newer table than the one paraphrased in the question you link, and it frequently doesn't go high enough for martial characters. You can try to extrapolate, but the table is geometrically increasing, so it will get big fast. The next step is obviously 16d8 but what comes after that is unclear.
This specific kind of build has a workaround
Strong Jaw functions differently if you are at least Gargantuan, doubling damage instead of increasing it on the path. If you can get your custom homebrew Strong Jaw item to emulate the effects of the spell rather than just letting you cast it, you can use Use Magic Device to count as a suitable race, thus counting as 2 less sizes larger, while doubling your damage. This is actually a bad trade in terms of just damage dice if you are off the table (4 steps on the chart at higher steps than printed should more than double your damage, since the end of the table does that exactly), but it keeps it in bounds longer and also doubles all of your damage modifiers, which is awesome.
This specific build doesn't need a workaround
A 15th level monk with your kit deals 12d8 damage. If he increased the damage he dealt by another step, it'd be a problem. As it is, though, he's still on the charts. Obviously, at 16th and higher levels you need access to epic rules (which don't exist for Pathfinder) to determine your damage.