From where I'm laying in bed and point at the door is about 12-14'. Will that work for me?
The rule of thumb is 1" of pattern for each yard of range. You have about 4 yards. Your pattern should be between 4-5 inches across.

The patterns above were fired with a full choke and 1 1/8 ounces of #8 shot.
>>From where I’m laying in bed and point at the door is about 12-14’. Will that work for me?
I don’t know. People think that a 18.5” shotgun will “fill a hallway” with buckshot. That is just not true. You’ll get a pattern of about 4 inches at that distance. You are using an unwieldy weapon in a close space where you might still be in bed. Furthermore, it has no sights. I gave up the shotgun for my bedside gun the first time I ever went and patterned it at bedroom distances.
At 12’ to 14’ distance the spread (assuming “open cylinder” - which is what a sawed off barrel will be), will be about 8-inches in diameter or so. So yes - a lot of .38 caliber rounds going into the perp - but you still need to aim. But easier to aim a short shotgun than a pistol.
And practice. And use buckshot. Birdshot at that distance will just piss the bad guy off unless you can hit him in the head, and maybe blind him.