Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Dallas/Fort Worth Airport to Saint Petersburg as you normally would.
Located just 8.7 mi from the city center, Saint Petersburg Pulkovo is the airport most travelers will use when flying to Saint Petersburg from Dallas/Fort Worth. Booking flights from Dallas/Fort Worth to Pulkovo (LED) should be relatively easy as there are 0 daily inbound flights from Dallas/Fort Worth from 2 different airlines.
Finnair and British Airways are some of the carriers that may have flexible cancellation policies. You can use our site to filter for other airlines that may also have this kind of flexibility.
Consider Finnair, British Airways or Turkish Airlines when booking your flight. These represent the most popular airlines when flying from Dallas/Fort Worth Airport to Saint Petersburg.