They can all come out of your paycheck. I do believe that the child support will stay the same even with the 401k loan. I would like you to do everything you can to avoid the 401k loan if you are able simply because if you for some reason lose your job during the 5 years the loan becomes a distribution and it's subject to the taxes and penalties of an early 401k distribution. Good Luck.

Yes, of course all three can come out.

You may not be able to withdraw/borrow anything from your 401k before the divorce is final without your wife signing off on it. You should check your plan documents to confirm this, and also check any interim court order that would bar you from spending down that particular marital asset. You don't want to be found in contempt of court by doing so.

All of the items listed can be taken out within reason.
Any borrowing or spending other than the ones you have listed will need consent and you need to run these by your ex before you do this. The best thing to do is speak to a solicitor to find out exactly what you are eligible to spend the 401k on and take all the paperwork with you. It is better to do your due diligence rather than being held responsible for some sort of fraud by the court.

Hope this helps.