You can ride through, you just can't stay over night and you're pushing it to stop to eat.
These things are obviously not so cut and dried.
There is nothing in the FOPA that says your passage through a state cannot include a necessary stopover to sleep or eat. Passing through some states it would be nearly impossible NOT to stop like that (and if your passage through is not in a motor vehicle ... hmmm... different thread...)
However the state you're passing through must not be your destination (or A destination), and intentional lingering, touristing, visiting, etc. would certainly call that into question.
What is important to understand about FOPA's safe passage provision is that it is an "affirmative defense." That means that you go ahead and violate state law by having those firearms, and if you get caught, arrested, and put on trial, you can then invoke FOPA and argue for your guilt under the state law to be absolved by dint of the federal law.
Several things to remember there:
1) You can absolutely still be arrested, held, and put on trial. Lawyers, money, time away from work, jail... You don't get that back just because eventually you will "win" the case.
2) The burden will be on you, once you've got your lawyer and you're on trial, to prove that your actions fell under FOPA. You will clearly be in violation of the state law, slam dunk case, and you must show the court that you met the FOPA provisions exactly and so therefore must be released. Those assertions you make will be rebuttable. If you say, "Your honor, I was just passing through..." and the prosecution says, "Your honor, he clearly was not! He spent 3 days visiting his aunt and seeing the sights..." (or, attended his son's basketball game at XYZ University...) your FOPA protection probably just disappeared.