You might consider setting your iFrame’s source URL directly using Velo:
$w.onReady(() => {
let var_1 = 'XXXX';
let var_2 = 'XXXX';
let var_3 = 'XXXX';
$w('#your_iframe').src = `https://www.videoask.com/${var_1}#variable1=${var_2}&variable2=${var_3}`;
});
Additionally, if your iFrame is embedded in a custom HTML element, you can also use Wix iFrame Messages to communicate back and forth with your embedded iFrame: