Hello AA community!

I am a Brit and BAEC Silver Card (OW Sapphire I believe) who will is flying on a couple of domestic AA flights (economy). Can you confirm if I can:
a) use the lounge at LAS and LAX and
b) I qualify for additional baggage allowance (and how much?)
Can I also guest my wife flying with me on the same booking and will she also get additional baggage?

Thanks in advance.