Meat – What cuts are “stir fry beef” and “stewing beef”

Some of your 'shortcuts' are not good ideas. Definitely start with cold water. Definitely bring up the temp slowly. Definitely do not boil. Do add aromatics upfront to the broth, but remove them as they get mushy so they don't cloud it.

Standard ratio for beef broth would be: 8 pounds of bones to 6 quarts of water to 1 pound of veggies (onion, leek, carrot) to one 'boquet garni', essentially garlic, rosemary, anise flavoring for pho, and bay leaf, plus whatever else I forgot.

If you have 'pond water', which I interpret as thin-tasting, you probably put too much water in the second time -- this is fixable by slowly evaporating out the water until it gets to a good texture. If you skimmed properly, it will be clear as you do this. I will typically strain through a kitchen towel or cheesecloth as the liquid evaporates down.

I'm guessing you put in like a gallon of water, so you had like three or four times too much water.

As a warning which you probably already know, you are not going to be able to duplicate your local pho joint's broth -- the broth recipe is the thing for pho makers, and they probably have a bunch of tricks they use, including using a neverending supply of yesterdays pho, that you won't be able to do at home. That said, you should be able to get a good beef broth if you follow some basic rules for making stock.

Try cooking on low instead of warm (or at a higher temperature, maybe 185-195F, with your fancy crock pot), and make sure you really got good stew meat.

I would expect the beef to have been reasonably tender after that long if it were the right kind of cut - certainly not inedibly tough, even if it weren't all the way done due to the lower temperature. But it's unfortunately possible that the beef for stew that you got isn't actually good for this purpose; sometimes stores will sell things under that label expecting (I guess) that people will cook them briefly in their stew. Make sure that what you buy has a lot of connective tissue that will break down as it cooks. See also What is the best cut of beef to use for stews?

If you did have a good cut of beef for long slow cooking, it's possible that 160F is still just too low (or that 11 hours isn't long enough) for the meat you got. See What is the lowest possible temperature for stewing meat? - apparently the collagen -> gelatin breakdown can happen even down to 130F, but it's much faster at higher temperatures.

It's likely that one way or another the low temperatures also messed with your vegetables. I'm not sure if that's actually hot enough to soften them. And for some vegetables, cooking them at a lower temperature for a while will cause them to stay firm even if they're subsequently cooked at a higher temperature!

There's a blurb about this in On Food and Cooking, which I'll find and add into my answer when I can. In the meantime, I found this in a Serious Eats article about carrots:

Unlike meat proteins which are fully cooked anywhere between 140 and 165°F or so, vegetables contain pectin—a kind of glue that holds its cells together and keeps it firm. Pectin doesn't break down until 183°F, which means that no matter what vegetable you cook sous-vide, you have to set your water oven to at least 183°F if you would like the end results to be tender ...