To answer your question,
1. No. There must be a warrant. If there is no warrant, whatever they find in your house or whomever they find in your house CAN NOT be produced as witness/evidence in court BUT this is malaysia. apa pun boleh.
2. No. Even if they have a warrant for your arrest, they are not supposed to hold your IC and force you to sign anything that you do not want to.
3. No.
4. No. Our laws do not apply to foreigners. They can only inform Indonesian Embassy. They can not arrest him/her for religious laws that only applies to Muslim Malaysians.
5. You can talk to a lawyer about this. The Malaysian Bar Council is a good place to check with. They will help you to defend your rights as a Malaysian who was coerced into doing something that you did not wish to do.
although PDRM 'walk sideways' and the law may not be able to protect you all the time, it is still better for you to talk to a lawyer.
by the way, i am a news editor. if you wish to highlight this matter in the press, i will be happy to help you.
Maybe I'm wrong but I think last time there was a muslim model from Singapore drank beer at Cherating and got caught and sentences for don't know how many canes.