score:4
To answer your questions, and for a little more info to add to jcaron's Answer:
1. I believe I have to pick up checked bags at the baggage claim in Terminal B, is this correct?
Yes, this is correct.
2. Do I need to carry all my bags to check in at a domestic terminal (likely T4 or T5) and check the bags? Do they have shuttle or train? Or can I use the overground tunnel?
Yes, you must carry all your bags to the LAX terminal from which your flight to DFW will depart. You can walk between terminals, and there is a free shuttle bus that runs 24/7 between terminals on the Lower/Arrivals level. You can read about these alternatives here. The overground tunnels are post-security; they will not be available to you as you'll be changing terminals while you are outside the secure area.
3. Do I have to go through security line again for the domestic itinerary?
Yes.
4. How much time I should reserve for this connection from landing in LAX to the LAX-DFW departure? I have to go through the non-citizen line at the Custom and Immigration.
I cannot improve on jcaron's comments here. Longer connection times are safer for you, as you're wholly on your own if the connection fails.
Upvote:4
As these are flights booked separately (a “self-connection”), you will:
TBIT to Terminal 4 is about 150 meters (one tenth of a mile), terminal 5 a little bit further. You’ll need to get from arrivals (lower level) to departures (top), exit the terminal, and follow the pavement.
You can’t use the TBIT to Terminal 4 connector as you need to check-in first.
Since AA has flights departing from TBIT (including flights to DFW, but those depart probably way to early for you to be able to use them), it may be possible to check-in there, though I doubt it (and AA check-in in TBIT is actually closed at this time).
Since you are self-connecting, if for any reason you miss the check-in deadline for your LAX-DFW, you’ll be considered a no-show, and your ticket will most likely be cancelled. You’ll have to book and pay for a new flight, at last-minute prices, which can be very expensive.
That’s why you should have quite a lot of buffer between the flights. 4 hours is the rule of thumb here (with the second flight being a domestic flight, quite frequent, and with hopefully reasonable prices), but the longer the better.