Problem is with the charger you're using. May be it's from manufactures other than your device's. It'll have different amperage and will affect your phone. You might not face any problems with charging via PC or laptop as it's current is lower as compared to normal wall chargers. Only I can say is, get a new generic charger asap.
Well there's two parts to that answer:
First, there were some issues with the touchscreen on the Lumia 535 when it first came out, but it's since been fixed.
Second, the Lumia 535 does not have a high sensitive touchscreen like some of the higher end Lumia models meaning you can't use the phone using regular gloves. You shouldn't notice this during regular ...
Sounds like you may have Super sensitive touch enabled. This lets you use your phone with gloves, but can be annoyingly sensitive if just using your bare hands.
To disable this, go to Settings → touch, and set "Touch sensitivity" to normal.
It is not possible to change single tap to double tap.
The problem that you are facing is very rare, probably you need to improve how you scroll and how you touch the screen.
When you want to touch: Gently put your finger on the screen for less than a second and then remove it.
When you want to scroll: Gently put your finger at any point on screen and ...
Go to settings => Personalization => Lock screen (at the end of the page you will see double tap for wake up
Sorry because picture is on my language
Update: For L535 go to Settings => Extras => Touch, you will see first option for double tap for wake up