Lmfao, we have Palpatine sending a wave of Force lightning into Kota's back, meaning again there was no barrier, and yet Kota wasn't incinerated. This is probably because Palpatine wouldn't instantly kill someone like Kota, he would torture him first (refer to Palpatine's torture of the Death Star designer). It's no surprise then that when Marek steps between the lightning, he's likewise not incinerated. Note that Palpatine probably never expected Marek to move in front of the lightning, hence why Marek could make a messily step forward. It would be foolish to try to ramp out the lightning from 0 to a 100 when Marek is only a foot away from him anyway, by the way.
We know he had back against Kota since Kota wasn't incinerated (noting that Kota didn't use a barrier either. The text states it hit his back and that he was completely caught off-guard). And note all three sources have numerous differences on numerous fronts. This being one of them isn't a surprise. However, your questions aren't relevant, since the text states it hit Marek's body, not his barrier or power.