First let me say I am no expert, only know what has worked for me.
With two and a half inches of fire you should definately have some heat! The fire doesn't sound like it is getting hot enough which could mean not enough combustion air or wet coal. I have never heard of putting a brick over a hole in the grate so you lost me on that one. Of course there are a lot of variables. What year and model stove do you have?
Things to try:
Make sure the coal is dry
crack a window near the stove to ensure enough oxygen
crank up the power vent a little more to pull more air
Make sure the combustion blower inlet is free from obstruction
It's best to try one thing at a time and observe for any change in heat output. My stove is an older model Alaska with the Tri-burner stoker which has the same motor driving the stoker as the combustion fan. I had to make a mod to that to add more combustion air by way of an additional blower, my heat output has increased and have little or no unburned coal.
Hope this at least provides a little moral support!