If you have the pelican 1510 then you're fine. Anything larger and you're pushing it. Check out the Dakine "Sequence" backpack.. it carries a ton of gear and is low-profile!
As for batteries you're fine too.. They're more interested in the 5 oz hair gel you've got in your back pack than the batteries...
Tripod.. again no worries. I've carried on some old school Bogen sticks w/ the 501 head a few times and no one ever said anything (TSA or flight crew.) Worse case scenario you might have to check it at the gate with the baby strollers.
When going thru security you will need to take your camera/laptop out of you bag (basic protocol), so I always send my camera through first followed by the gear bag. I think this helps reduce the shock of all the junk that comes up on the x-ray monitor.
btw - Southwest is very media friendly! I just flew to FL with three bags. Two of those were 60+ pounds/over sized and they were going to charge me $180... I told them it was "media" gear and they just charged me $25 for my third bag. Coming back the lady was too lazy to charge me, so she just let me skate!
> Media cameras are exempt from the sizing box restriction imposed on other carryon luggage, and, if carried onboard, must be stowed in accordance with FAA safety regulations. If the camera is to be secured in a seat, however, a ticket must be purchased for that seat.
> Camera, film, video, lighting, and sound equipment will be accepted when presented by a representative of a network or local television broadcasting company or a commercial filmmaking company. A fee of $25 will be charged for each item in excess of the free baggage allowance. Media equipment will not be assessed oversize or overweight charges.