Can I get scriptures that support baptism as part of salvation besides Mark 16:16?

What is the correlation/connection between water baptism and church membership? I see where Acts 2:41 references both baptism and adding to the church in the same context, but have not found where baptism is clearly required for church membership.

When it comes to spiritual things, people often fail to keep a biblical balance. This results from partial knowledge of doctrine. The requirements for salvation in an individual are no different.

There seem to be a difference in the names of the twelve disciples found in Mark 3:16-19 and Luke 6:13-16. The only solution for this contradiction is to ASSUME that Thaddaeus is Judas. Do you have any proof of this?

How old is threescore and in 1 Timothy 5:9 does this mean the church is not responsible for widows until they reach this age?

Many people have taught the idea that there is an age at which a child becomes accountable to God. Is this a scriptural teaching and if so, what age would it be?

What does Acts 2:38 mean and does it apply today?

In Acts 26:28 the King James says that Agrippa was almost persuaded, but the NIV says something completely different. Can you help me with this?

Is it true that they were not in the originals and if so doesn't that mean they are not inspired?

There are genuine questions concerning the preservation of the scriptures into English. Is it necessary to find the answers to all of the problems or should we just trust that the Lord has preserved His word?