If you have home internet and a wireless router, have you tried activating Wi-Fi calling in your phone, most newer phones support this. This feature was introduced to phones to use a home internet connection to make and receive calls and text messages in a home with poor cellular connectivity.
Yes you can but you at least need a signal inside for it to boost. I bought a SureCall EZ4G but it is an older Verizon model that only gets 4G(no 5G here yet) and it works for me. The one that SureCall sells now is an updated version that says it gets 5G also. I didn't know at the time I bought mine off eBay but the instructions do say you need at least a low signal of -100dBm to a high of -90dBm for it to work which is about 2 bars, I am around -117 dBm which is one bar of signal but it does boost mine up to 4 to 5 bars but it is limited to my living where I have the output antenna. This one that I have the receiver you put in a window with the best signal either using the adhesive or the stand, the receiver dish is kind of huge. You need at least 30 feet of separation between the receiver dish and the output antenna, if less then you need a wall or two to separate them or you might get interference between the receiver and antenna. Since my signal is weaker than recommended lately I have noticed the signal drops from 4 or 5 to 1 now and then and not sure if it is my new phone because when I got it 6 weeks ago the old phone didn't do that or didn't think it did. This antenna is an alternative to mounting one outside to boost the signal.