I certainly agree with all you state; it's a great logical reasoning behind your thoughts. However, for the sake of argument, and definitely not to contradict or refute your statements, but more in the spirit of sharing thoughts:
An important question which arises is, "What if I am punished for
worshipping the wrong diety?" Clearly, everyone can't be right at the
same time.
I'd say, not that clearly. There are several religious organizations (granted many are very modern) that don't believe that they are the one and only way of reaching their god. Also, I've known of some christians who are human enough to let others (including in their own families) worship and are happy that other behave according to their morals and religious believes, even though they don't share religious denominations.
Also, using your same reasoning, their God may want things that way, as ultimately he's supposed to be the one deciding who goes to heaven and who doesn't.
Therefore, it is pointless for one religion to claim
superiority over others when it may also be wrong. Many theists feel
that only atheists and agnostics are at risk of punishment.
That is based on the premise that the one and only reason people join a religious organization is for salvation. That is far from the reality. Sociologists, psychologists and other professionals in the matter agree that many churches are social clubs. People join for the after school programs, for having a healthy atmosphere for their families, to join other families that are expected to be decent and with the same set of morals, to participate in dances, retreats, and other events that are organized by the church, to dress nicely, to be invited to weddings, and the list of social reasons goes on.
Also, there are many different reasons why people join and stay in a religious organization. Many of them have to do with staying away from certain crowds, to maintain sobriety from alcohol/drug abuse, to find a decent mate, to mention a few. Many people really can't care less about salvation, not even doctrine. They want a sense of support and safety.
Then there are the "Christers". That term was introduced to me by my husband's sister. A Christer is a "Christmas and Easter only Christian". Some people go to church, and consider themselves part of it, even though they visit their religious organizations in special events, such as weddings, funerals, Easter, etc. Those can't care less about salvation either. I consider those the "cool Christians". Those tend to have a general believe in the church's teachings but live and let live.
Along the same line of the Christers are those that I call "christian by ethnicity". There are a lot, and I mean a lot, of people who go to church because it's family tradition, and because it's what their community/culture does, and they only go for a sense of belonging to their culture and/or community.
As for the superiority, only a few, and those tend to be those cult-like organizations, like the WT, are the ones that blatantly teach that they are the one and only entity in god's favor. If you notice those who feel superior for being Christian or for having "the truth", or for being "saved", are people who stand out from the crowd of their congregations for being that way. Their religion doesn't teach to be superior (there's an entire psychology behind the superiority feeling for being "chosen"). Those traits, the propensity to be, feel and act in that superior way, exist in the person that chooses to do so. The religion is used as a catalyst or trigger for what already exists in the person, unless it's a cult or cult-like religion that promotes that, then the entire congregation is encouraged to feel and act superior.
So yes, although I definitely agree with your statements, I believe that there's more to the story.