Hi @L1111. -70 is a pretty high RSSI. We have this Community post here that explains RSSI in depth. Generally, an RSSI of -60 or better is what I consider acceptable. With proper placement of a Chime Pro, you should be able to achieve this! I recommend buying the Chime Pro from Amazon so you can take advantage of their return policy if the Chime Pro doesn’t work in your favor.
Another thing to consider would be the outside temperature. In the colder months, you can expect to have less battery life due to the nature of batteries performance in cold weather. You can also add a Plug-In Adapter to add a trickle charge to your Doorbell. I’ve done this a few months ago and I haven’t had to charge my batteries yet. It did require a bit of drilling to run the wires, but it works well.