Over filling

Let me thank you folks real quick for helping me get started this season. I was nervous, you guys knew it, I learned a lot and my pre EPA has been a godsend. I dont know how I got by without it.

Starting out with little fires and getting ansty when the Rutland Flu thermometer got too close to 500. I was on cloud 9 when I mastered an overnight burn waking up to a warm house and . And now with the right wood, I can keep her simmering while I'm at work all day too.

Which brings me to my question. Is it safe, not a good idea, or normal... to load this up to or past the flu outlet?
I've been doing it... and the other night I got up to take a leak, (by the way I've never got up in the night and had to stoke it, it just holds out and keeps the house warm till morning). But the other night when I got up, I noticed it was chillier then normal in the house but still comfortable.
I could see slow lazy flames through the glass, and I wondered if it was THAT cold outside that the stove was not able to warm the house any further.
I looked at the Rutland Flu thermometer and it was at 625° ...not what I wanted to see, and it was already dampered down to the 2/7 position. I closed it to 6/12 to get it back under control. Never having those temps prior, it made me extremely nervous, and now I'm wondering if I over filled my box, and have been this whole time, did I have a small chimney fire...
Remember I'm running an ole Homesteader.

Thanks guys.

jjs777_fzr...the flu thermo sets right on top of the highest horizontal piece of the black pipe elbow in that pic.

pen...This one has steel inner plates which end at the bottom of the flu exit inside. But there's a lot of space above that.
I'm fairly confident the ash pan and the loading door itself are sealing. I could use a incense or something to test it, but the stoves in incredibly good shape and I did rework all the locking levers etc to get it to draw down tight when latching the doors. The gaskets are good.
Getting an overnight burn is no problem. Even since this incident, I stopped loading past the flu exit until I could find out if it's a bad idea or not, and I'm still getting overnight burns.
I just wasnt sure if I should be loading past that flu exit or not since that one weird night with high flu temps and a chili house. Never had that happen before.

Got it.
Again I cant thank you guys enough for the sound advice going into this, this year. Much appreciated.