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.
Roasting the bones will give you a darker brown stock than using the raw bones. To roast the bones, just stick them in an oven on high heat, around 450 for about 45 minutes, or until they are a nice golden caramelized color. Though you will want to make sure to keep an eye on them the first time, I'd check every 5 minutes after half an hour. Roasting the veggies with the bones will also add a slightly sweeter roasted flavor. It's like the difference of putting slices of raw onions on a burger compared to caramelized onions. You get a slightly sweeter, richer roasted flavor. Though it does turn down some of the other flavor notes, it's up to you which you'd rather have. Without roasting, you'd have a clearer "white" stock.
If you are using the butter as a base to roast the bones, I would set it aside and go with a higher smoke point oil like a peanut or corn oil. The low smoke point of the butter could leave a bitter, slightly burned flavor, especially with the longer roasting times.
I would leave the seasoning for the stock. Most spices will burn at a lower temperature, and salting the bones before you make your stock, could make your stock overly salty. It's easier to add more toward the end, than try to figure out what to do with salty stock.
I hope that helps!
Best Answer
Taste the meat and if it still seems edible to you then there is no reason to throw it out.
When I make stock, I keep it on a simmer for much longer than three hours and any meat is completely tasteless by the time I'm done. Three hours, however, is about how long you would cook meat to make a stew, so it's quite possible that you could eat it.
On the other hand, not all cuts of meat stew well and I'm not familiar with this cut. If the meat has plenty of connective tissues (i.e. collagen) to gelatinise it shouldn't dry out too much. But the proof is in the pudding: taste it.