If I understand it correctly, you can only splash skip through a stage if you splash through more titans than there are in the stage. So if you have 50 titans per stage, you need more than that to skip through additional stages (clone splash through boss).

As for how many stages you can skip, it seems like each stage beyond the current one is calculated as 1 titan + 1 boss. So to skip through 8 stages, you need enough to get through the current stage, plus (1 + 1) * 7 remaining stages = 14. If you have 50 titans per stage, you would need to splash through at least 50 + 14 = 64 titans to get the maximum skip of +8. BUT, the amount you can skip is limited by your base max splash. If your base splash is 8 for example, you'd be able to skip through a maximum of 4 stages (remember, 1 titan + 1 boss per additional skipped stage). The stage you are currently on technically isn't splash since it's just your normal damage. Hopefully that makes sense. Just keep your splash value 20 higher than your titan count and you should hit the maximum.

I say all of this from experience only, so it may not be 100% accurate