Staking/node privacy-secure?

Currently im staking an "X" coin and its doing pretty good regarding staking.. at this moment devs of X coin released an article on how to setup a node and im stuck because i don't understand some things if you could help me that would be great.

I'm using Linux and before running a node from private computer below are devs statement from article they published and my questions.

Devs statement

1. Do not use your public node to store your "X Coin" or for staking. Stake from a separate computer, if possible.
* What happens if i store X Coin , run a node and staking in same Computer?

2.Your firewall should have a single port (xxxxxx) open to the outside world, and physical access by unauthorized users must be prevented.
* Would it be possible for someone to access my wallet through nodes and spend X Coin?

3. Do nodes cost electricity?

4. If i run a node would it be more profitable than staking?

I'm not interested buying hosted nodes.

Thank you.