Couple First Time Visit Advice

Hi there, I love the idea of watching my partner playing with someone else, however we’ve never done it before and we’re slowly exploring the idea, hence this post. I’m 34 top & he is 30 bottom.

We’ve never been to a sauna or even had fun with anyone else, however my partner and I have discussed this recently and we’re not considering visiting the sauna to have a bit of ‘fun’.

We’re gonna ease ourselves into it, but we both like the idea of my partner playing while I watch or join in (if comfortable). I’m thinking initially we would visit the glory holes, that way we keep some anonymity and we can slowly try more, if we like it of course.

My questions / concerns are:

Are there any rules against me being in the glory hole booth with my partner, just purely to watch him sucking?
How does one go about saying no to a cock offer in a glory hole?
Is it generally safe to swallow and do we assume that most guys want this and comfortable with it?
What is the main etiquette to know prior to visiting and anything we should know or be on the lookout for?

Any advice would be much appreciated.