Yes, taking a reasonable amount of time to review a major career decision is normal.

You do not need to justify every hour of the decision period. What matters is respecting the stated deadline and communicating early if you need an extension.

You can thank the recruiter, confirm your interest, and say you would like a few days to review the offer and discuss the decision with people important to you.

If the existing deadline already gives you enough time, use it. If not, ask for a specific extension rather than leaving the timing open-ended.

Totally reasonable. You are making a job decision, not ordering lunch.