This is an awesome thread. Great to see us talking about playing and not just abusing our wallets ?
As for how to practise intervals, I think the video Adam posted is a brilliant way to do this.
So here's what I would do:
1. Get the
ChordBot app for your phone. It's free (I've paid for the premium version - WORTH IT).
2. Make a simple 2-chord tune. Make it loop endlessly.
3. Make a diagram of a single position on your fretboard. Copy it so you have 2 copies.
4. Mark down the notes for each of your 2 chords.
5. Plug your phone into the AUX of your amp, so you can hear the backing track nice and loud.
6. Watch the video again.
7. Play, and see how each interval "interacts" with the chord beneath it.
Keep doing that for a while and then maybe add a chord after a few days. Till eventually you have a whole progression going (12-Bar Blues maybe).
Also, on your diagram, it would be wise to not just mark the actual note positions and note names, but the interval names as well.
So for example, a single dot might have the letter "A" in it or next to it, along with it's interval number, like "b3" (flat-third) or whatever.
So yeah, that's how I'd practise it. This gives you an easy way forward and
ChordBot is fun and really flexible. You can make your backing track as simple or complicated as you like.