There are no pellet stoves that burn wood and pellets, however quite a few now burn wood or Corn,
Very few pellet stove continue to run after the power goes out, if they do they are top of the line models, and come with a backup battery, and that usually is only enough power to let it go through you cooldown cycle, so that all the unburned pellets get a proper burn, then the stove goes out.
If the chimney you had can be relined, they put in a flexible liner, and a filler around the outside of that pipe as an insullator. check with your fire codes, most require a minimum clearance or thimble anytime a pipe passes through a wall/floor. They make a 2100 stanless triple wall pipe that should meet or exceed any fire codes, but it isnt cheap. Check with a local chimney sweep, they can evaluate your old chimney, who knows there may be nothing wrong with it.
Wood is the way to go if you want something that continues after the power goes out.
Pellet stoves are better in cases where want heat, but dont want to have the hassle of flue pipes. They only require 36 inches extended away from your house, where most flue pipes are required to extend a certain height above house/ or above the nearest flamable section of the house, the chimney sweep should have a formula of how high it must extend.