So I've been teaching myself for about 7 months and I'm not all that certain I improve in the most efficient way possible so I'll list a few problems and any feedback would be much appreciated:

1 - Sometimes I'll play a song fairly accurately and other times it's much less than perfect; Is it safe to assume that accuracy and consistency will come through practice, practice, practice, or is there more to it than that?

2 - Almost every song I've attempted to learn at present is by Parkway Drive -
The 3rd to 7th fret stretch is impossible to do in a musical fashion as in, I can barely make the stretch past the 6th fret with my little finger and index on the 3rd and I definitely can't make that transition in a song...so: Specific stretching exercise? Or just keep on playing and it will come?

3 - So far I have learned by learning songs because, it's enjoyable and sort of gives me a feel of where I'm at, but like I said previously, is this the most efficient way of improving? - I'm constantly trying to perfect the same songs because I don't want to be able to sort of half baked misplay 25% of the notes and say I can play a song; And so the only 2 songs I can play the entire way through with I'd say minimum 90% accuracy are 'Alone' and 'Home is for the heartless' - Both by PWD.

4 (Misc.) - Can't work out pinch harmonics in the slightest, I feel as though I'm almost picking with my thumb at the same time as the pick? --

-- I'm about to make the upgrade to an ESP LTD EC-1000 Deluxe, I tried one out and in comparison to the guitar I've been learning with, it feels far more fluid and comfortable to play, may even solve a few of the problems I have with harmonics etc?
(String action on my current Guitar is pretty high )

TLDR?: Questions are in bold

Thanks in advance.
1) Consistency comes with practice, confidence & time
2) There are loads of stretching exercises. Look online & you'll find one. Try playing the pattern an octave above & work your way down a fret until you can play it.
3) I found learning songs to be the best way to learn until you are trying to master a specific sound/technique
4) Pink harmonics can be done on an acoustic & the guitar shouldn't really impact how you do them. It will make them sound better & have more sustain though