How did you select that handgun?  I looked up the price (at 
www.gunwatcher.com ) and I see that a S&W Shield goes for $85 more than a Maverick 88 (12 gauge 18.5" barrel) which would be vastly more powerful.
Back in 2016 I bought a short-barreled shotgun just in case I ever needed it.  I saw my father die a slow death in home hospice care and always thought that he would have been better off if he had ended his life with a shotgun.  I too am very nervous, knowing that I must CTB yet being unable to make that happen.  SI is real bitch.