If I transfer BTC to a friend/family, they now know my wallet address, correct? Does this mean they can see all the transactions I have done from that wallet? It seems like wallet information is public except for identity, but that would be forfeited once I make a transfer, right?
You wouldn't be so alarmed if you just didn't do any transactions to a porn site.

Yes they may see all the transactions but you can always reason.
Seriously I also worry but it looks like they are yet not interested in such things as checking out how much BTC I have in my wallet or what transactions I do with the wallet I have.
Spreading out your BTC to a different wallet or just send altcoins to them. I do trade which is why I just send from an exchange wallet whether BTC or altcoin. If they check that wallet out, they'd really assume I'm the richest.