<human>: Summarize the given text in a few sentences.

I'm flying for the first time since I was seven to see some family that moved away a few years ago, and because it's been so long I desperately need some advice. 

So here's my back story: My flight was a gift from family, and I'm staying for a month. I'm flying United Airlines out of LAX, and have two layovers in states I've no experience with (Chicago & Wisconsin) and I'm kind of freaked out from all the horror stories I've heard of missing luggage from getting baggage checked, so I was hoping to get some opinions/stories/experiences from everyone. In a perfect world I would just take my two free carry-on's, but I might have to check luggage due to camera head.

Checked baggage questions:
Do I run a higher risk of my baggage going missing with so many layovers? 

Should I lock my bag? I've heard the TSA will just cut the lock to check it if they need to (and they might, I'll have a disassembled camera tripod in the checked bag, might look weird through an x-ray to them)

Carry on questions:
Speaking of tripods (25" in length), is it possible to to just carry the tripod onto the plane in addition to my two personal bags? I couldn't get a straight answer from the airline. They basically said it will be up to the person letting me on the plane, but I'm doing everything solo and I can't gamble a $300 tripod being checked without a bag if they say no.
<bot>: I'm flying for the first time with a bunch of layovers, what's the likelihood of my baggage going missing?