I am not familiar with the Pepwave, but updating the radio is a good start. Look for deals to update your other one I suppose. I can't say enough positive about 4x4 MiMo on midband given the right environment. I will look at your hardware more today and see if I can offer you any input. Radios are kind of flux right now since we are peaking on LTE, I am working on getting some 5G radios from China as soon as that place stops exploding with virus, they would come with a Cat 22 LTE radio underneath the 5G New Radio radio.
Any of the radios from Telit like the LM960 and up are going to be good, their FN980 is just now getting to engineering samples being dispersed. The upcoming EM20 from Quectel is going to be pretty sweet. I have been building out a lot of those lately with the engineering version, a fren has a peak speed of close to 385Mb p/s using Sprint with one sitting in an ZBT WG3526 router, over PoE. 4x MiMo and 3 carrier aggregation.