I want to sign my rights as a parent but i dont want to pay child support is this possible in washington state?

Once you have a child biologically, the law requires payment of child support.

My 16 and 14 year old want to go on vacation in hawaii

There might be huge problems with the scenario you describe. You should get a parenting plan or residential schedule.

Maintenance. Can I make motion after Judge has ordered me to pay $500./mo. Even though I showed I cant afford it.

There are ways to ask a court to reconsider or amend a judgment. See CR 59 and...

Can my ex contest an amended petition if he is in default?

A default only allows the court court to grant the relief requested in the petition.

Is it WA state policy that if CPS takes your child once the 2nd time they cannot return the child home?

You can ask CPS directly about their policies: https://www.dcyf.wa.gov/services/child-welfare-system/cps

The legal remedy for failure to obey a court ordered parenting plan is a motion for contempt.

See https://snohomishcountywa.gov/715/Family-Support

Can you bring up new but relevant info on cross?

There have been arguments about cross-examination exceeding the scope of the direct examination. Thompson v. Henderson, 22 Wn. App. 373, 591 P.2d...

You mention lawyer fees - talk to your lawyer. Perhaps a motion to compel discovery would be appropriate. Motions for continuances are common.

You can make a motion for amendment of the judgment pursuant to CR 59 or...