For the flange I would use two large pipe wrenches. But would wait unit your torch at home and the a extra female sweat to male threaded elbow just case you damage that one. As for the auto bleed don't remember ever seeing any you could take a apart and clean. Most are crimped together. Seen some large auto bleeds for commercial boils that bolted together. Almost everything I worked was chilled water. Large system would have a ball valve to remove them. Can't see why there code against it on heat water. Most commercial building here use eletric strip heat. Home either natural gas furnace or heat pump. Our cabin has a electric furnace. I have a heat pump with back up strip heat to install. I plan to play around to figure the temperature the heat because worthless in the winter.No natural gas available and with the wood stove can't see going propane. With the size of the cabin and the layout I can load it in the evening and it only be in the mid sixties when we get up. But only when the temperature are no lower than the twenties.
The Toyota 5.7 uses the same setup except the cover is plastic and threads into the block. In the end is a metal plug to drain the filter before removing to reduce the mess. Of coarse the plug was so tight the whole cover just spun off. Since I planned on leaving town I didn't mess with trying to get the plug loose. Murphy's law if I would have tried getting the plug loose the housing would have cracked and would needed to be ordered. Second time around I was able to get it loose without breaking anything. On the 4Runner I was afraid the oil leak was caused by something I did off road which wasn't the case. Original plan was my youngest was going to drive. I'm lucky that didn't happen as my daughter has a history of ignoring lights on the dash and destroying a engine. I fixed it and only needed a fraction of quart to get it full, oil was still with range on the dip stick. When I replaced the CV axle I stretched the wires for the ABS sensor to tight and broke at least one wire.