Your data contradicts the idea of any "even split".
It splits it into three camps;
"legal without any restrictions" at ~29%
"legal with some restrictions" at ~50%
And "banned completely regardless of circumstances", at 20%.
The status quo, that was set by Roe V. Wade, is that middle category. People who think the current law on abortion is fine, or should be even more accessible, they make up ~80%. Those who want to overturn Roe v. Wade and apply greater restrictions, they're the 20%. No more.
Even if you want to flip that around and try and argue about the 29% as if the 50 and 20% were a combined "side" (which is ridiculous), that's still a 70/30 split.
Your data source contradicts the idea that there is any kind of even split about abortion, in the USA.