In response to your question.
1. A master prblic key knows the addresses the master private key (what you don't see) is going to produce. Both of these come from the seed but the master public key has no control over the bitcoins.
2. Yes, you can restore everything from the seed.
3. No change_gap_limit should keep generating your addresses. You'll run out of addresses if you don't do that (as an unreasonable number of change addresses will be used that your wallet don't have if offline and not setting a gap limit).