Question #3. Yes, I got a boar - after 5 seasons of hunting.
Question #5. I used a 338wm with 250 grain Swift AFrames, did the job. That was the only AFrame I ever recovered. The bullet stopped just under the hide on the far side after plowing through his boiler room.
Question #6. I'm not sure what eastern black bear hunting is like, but hunting interior mountain grizzly was, for me, a difficult and challenging hunt. I hunted the mountains and valleys west of Williston lake, the odds basically guaranteed your getting a draw. I hunted hard for 4 years, first getting to know the area and then putting the effort in. We would glass slides, openings on the mountain side, etc. When we saw one we would put a stalk on (by the way, that green area that looks like a golf green from the road is not - it is a willow and boulder covered mess and a bi$#tch to walk in) most of the time the bear would smell, hear, see, or somehow sense us and go away. Meanwhile we just walked halfway up a mountain again. However the scenery was beautiful, the exercise was good for me, and it became a part of spring for a few years.
The one I ended up getting was on the last day of year 5. It would be great to say it was a master stalk but in all honesty I was checking one last time a spot where we had seen a lot of sign, on the way up there he was standing in the middle of the road as I came around a corner near where we were going to start scouting. I got out, he took off, at the edge of the clear cut I yelled at him, he stopped and turned around to look at me, I put one through his boiler room.
Then he took off like I hadn't touched him.
We sat down and waited about 15 minutes and then went into the super thick bush he had run into. I will say my heart was hammering as I went into that thick bush - but we had to, couldn't leave the job not done. There was a blood trail like someone was pouring a 5 gallon pail of paint out on the ground and he was piled up under a tree about 25 feet into the thick bush.
I think grizzlies are a good deal smarter than a black bear and several times stronger. One of the most challenging hunts I have ever done.