A hydrocarbon resource recovery system is for hydrocarbon recovery in a subterranean formation. The hydrocarbon resource recovery system may include an RF antenna within the subterranean formation for hydrocarbon resource recovery, an RF source aboveground, a coaxial RF transmission line coupled between the RF antenna and the RF source and having an aboveground portion, a dielectric fluid pressure source, and pressure members joined together in end-to-end relation to define a pressure housing coupled to the dielectric fluid pressure source and surrounding the aboveground portion of the coaxial RF transmission line. The pressure members may include a straight tubular pressure member, and an elbow pressure member coupled thereto.