Hi!
1. The position is automatically calculated by the jquery UI script in this case. Maybe adding some padding there might help, but it should always try to display it within the viewport if possible. Adding margin/padding may affect the calculation negatively and make it worse, I am not sure about that. I would rather recommend leaving that as it is.
2. This is indeed a mobile thing, but there might be a way to prevent that with a custom script code, by changing the inputs for a read only mode. This may not work in all cases either, but it’s worth a try. Try adding this custom code to the functions.php in your theme/child theme directory (copy from line 3 only!). Before editing, please make sure to have a full site back-up just in case!