Re: I just lost Jack's loyalty to keep Amanda's
First, I assume you mean Miranda instead of Amanda.
Second,
If that is true it means you had too few Paragon to be able to choose the Paragon answer and this is, at the time you can play Jacks loyalty Mission, one of the more easy achievements in the game.
To keep both, Miranda and Jack loyal, you need a nearly fully filled Paragon OR Renegade bar.
The game lets you get away with many moral system choices if you did not fully embrace one side, paragon or renegade, but not with all.
Or in short, to keep them both loyal you need to decide on one moral path, you can't be good in situation a. and bad in situation b. (Or only in very few situations.) because you will not get the necessary paragon or renegade points you need.
Because you're on a PC you could use the "Trilogy Save Editor" found on the NEXUS to gave you the amount of paragon or renegade points you need.
For game advise, there is the Mass Ef fect Fandom WIKI, which holds a enormous quantity of knowledge about the games.
There are also, besides the YouTuber you mentioned, many many other YouTuber that streamed full playthroughs of the games.