I'm still not sure what kind of leads you're aiming for but you got some good advice about hearing it in your head and precise timing. Some of the best advice I ever got was to stop "just practicing". Think what you play, even if it's just running scales, it's still your voice.
I think, and my opinion is a humble one, that leads are made out of melodic ideas, and devices or ideas about how to use the scales and chord notes. Certain devices seem to belong to one sound or style. Once you form some of these general ideas it's easier to learn the scales and shapes, and have ideas with them.
For example, starting with that f-chord, you can make a particular kind of scale by starting on the note one fret below, then hammering onto the chord note, and it has an odd climbing feel as you go up and down. It's a device of passing from an off-note to an on-note. Then, once you have the notes of a scale, say the f to the g note, you might use the f# inbetween as a passing tone. That, and the slide-up note gets used a lot in rock leads and riffs.It doesn't have any lingering melodic value--usually--but is sort of an energy thing, used to create a tug.
One simple way to start to look at scales is they are generally the notes in your home-base, or key-chord, plus linking or step-notes that are in the other chords in the key. What's good about that way of looking at it is you link the step-by-step way of looking at scales to seeing the shapes and bits of the other chords, and that helps because while you play, the chords are changing.
people can put any chords they want in a song, some songs aren't even exactly in a key, and sound right, so when you learn basics they may not work everywhere. But I guess my point is to try to see the general idea or the musical effect in the bits and pieces you learn, and you learn a lot more than a lick or two.