Good morning, Renee. I hope I can provide some helpful responses.
Prostate size is reported in "cc's" (cubic centimeters). During the biopsy, the doctor uses an ultrasound to get several dimensions of the prostate, then uses a complex 3-dimensional formula based on the typical shape of a prostate to calcuate an estimated volume. 23.1 would be a fairly normal sized prostate...which is about the size of a walnut.
The aggressiveness of the samples found in the biopsy, as indicated by the Gleason score, is low, which is a positive factor; although one always has to keep in mind that a biopsy is simply a sampling. Each sample represents only about 0.1% of the prostate.
With the number of cores positive for cancer, and the percentages of cancer in those cores, you husband would not be a good candidate for Active Surveillence, which defers treatment for a little or a long time (or forever). An aggressive treatment would be appropriate, but that doesn't mean that it need to be rushed-into tomorrow. Prostate cancer is different from other cancers and is generally slow growing. With the understanding that aggressive treatment would be appropriate, one should move deliberately, but not rush, into a treatment decision.
With surgery, the experience of the surgeon is generally considered to be the most important factor to consider. There is a well documented "learning curve" in the surgical proceedures to remove the prostate, and you would want to find a surgeon who has performed many hundreds of prostatectomies.
I hope this answers the questions you raised. Please don't feel the need to panic, but do help your husband to move forward deliberately with an examination of treatment options.
best wishes...