Hello,
My BIL has an Aldera T5. The stove works fabulous. EPA stoves burn front to back and then the coals. I burn pine and most of the heat seems to be the coals, not the flaming wood. YOUR problem is weak draft. I run a lopi answer and I've been fighting for years because of a compromised install. I'm running a 6" SS liner through a 6" by 12" tile liner. The SS liner touches the tile an is forever cold. My stove exhibits same problems yours does. I've insulated my liner as best as possible and I finally got the stove to function but its still not great. My BIL stove is a dream to run in comparison.
He is using a strait up double wall class A or whatever they call the modern insulated high temp stove pipe. His stove lights off easy and burns great. Again we burn pine but the trick to making it run is as soon as the fire is lit and growing make sure the door is all the way closed and sealed. once the wood is burning good and the stove is full of lots of BIG fire move the air control to the middle. He has a thermometer in the left front corner of the stove top where its easy to see from the top through the grates. Watch this thermometer, once it gets to 400* move the air control all the way to the right, closing it all the way down. The secondary burn will be a blob of flames just hanging out in the middle of the fire box, its very mellow and very stable. It just kind of floats there. From this point on don't touch the stove until all the wood is burned down and is most of the coals. He doesn't bother raking the coals around too much during reloads either. The thermometer will creep up to or just over 600* by the time the wood burns all the way up. He wont refill until the stove top is less that 300*, although this will vary depending on how much heat you really need. If he doesn't refill it, it will eventually consume almost all of the coals leaving just ash. The glass always stays clean.
This is how he runs it and gets it up to operating temp the fastest. This stove wont build much heat until the air control get turned down some and the secondaries start doing something. Also this stove never smokes, ever, when he runs it like this. His neighbors even ask why he never uses it because it is so clean. His stove also seems to work fine with or even prefer larger splits. Dry wood is very important but damp wood doesn't cause the problems that you describe.
If I understand your install you run the short section of strait pipe up to the elbow and then run it horizontally into an existing 7"X7" tile liner? there is not another 90 and liner up through the existing 7"X7" liner?? If this is correct then "DING DING DING WE HAVE A WINNER". That is your problem. You need to run your flue strait up and it needs to be the insulated stuff that your running inside. This is what its going to take. Period. I've been fighting the same problem for many years, it will never be right unless you run the insulated stuff for the whole run. Trust me I know.
Get the stove a proper draft and you will absolutely love your EPA stove. They never smoke, burn less wood, and from what I've seen, are easier to run.
Bullittman