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.
I go into a lot of detail regarding steakhouse quality steaks in my answer here.
Excerpt:
Any steak you buy in the grocery store is minimally wet aged. The finest steakhouses dry age their beef. The difference? Wet aging consists of simply vacuum packing the meat (as in a whole side of cow) and refrigerating it for about a week. After that, it's cut smaller and sold to stores. Dry aging is a more complicated and expensive process. Dry aged beef is hung for at least two weeks in a refrigerator. Moisture in the meat is allowed to escape and evaporate, which concentrates the beef flavor of the beef. The beef also grows a moldy rind which is cut off and thrown away. After the aging is complete you're left with 75-80% of the meat you started with. This commands a premium price.
Please note that the dry aging happens long before you purchase the steak. The entire cow is dry aged before it is even cut. You cannot truly, safely dry-age steaks in your home. There are refrigerator aging approximations, but they are just that, approximations.
Best Answer
Here is what some will definitely label a biased description of aging and packing that might help a bit. It goes into the difference between wet and dry aging and gas packing which has become more common.
My description of dry aging, and wet aging for that matter, and how I was taught to think of it is that it is decay, but controlled. Enzyme action breaking down tissue for a more tender product, and and improved and more concentrated flavor is the goal and this enzyme action is definitely decay. As to bacteria, even the above article a supporter of aging, in its description of dry aging points out that the outer layer absolutely is contaminated by bacteria.
Also, the dry aging is done at 30-35 degrees (F), an area of slow bacterial growth and outside of the 40-140 (F) danger zone of fast growth.
Wet aging is also done, or at least should be, at these same "safe" temperatures and is normally done is vacuum sealed bags so should again not be high risk for contamination. Dry is at more risk because it is in less sealed environment, but is also high price/high value so tends to be carefully inspected and cared for. As normally 10-15% weight is lost during dry curing, and additional is lost to trimming for safety, plus the additional holding time and handling, prices are much higher.
ETA: Their description of 10-11 days for dry aging I would definitely put at the low end of premium aging. All descriptions I know of that is about the limit of water loss, but only the beginning of some of them big changes in flavor.