Antenna recommendations?

correct

The antenna is a full half wave dipole which has by definition a gain of 2.15 dB above a isotropic antenna (which is imaginary because it can not exist in real world.)
2 meter of RG174 gives - 0.6 dB

So the gain is 1.55 dBi (2.15-0.6) so the claimed 5.4dBi is a fantasy which I would not expect from a product sold by Digikey

see: Isotropic Antenna - an overview | ScienceDirect Topics for the mathematical background