Something that helped me break through a plateau around your level was splitting my times by step before deciding what to practise. Do a few Ao12s and note roughly where the time goes — for sub-15, cross around 2s, F2L around 8-9s and last layer around 4s is a decent shape to aim for. Whichever step is furthest over its target is the one to drill that week, instead of trying to fix everything at once.
For lookahead, the drill that actually moved the needle for me was a short block of untimed solves where the only rule is no pausing: turn as slowly as you need to, but never stop turning while you track the next pair. It feels really slow at first, but that's the point — timed solves mostly just reinforce the pauses.
One more thing: pick one thing to count for a week, like how many crosses you fully planned in inspection, or how many F2L pairs you solved without a rotation. When the average isn't moving, seeing that number climb is what keeps you going. Sub-15 is closer than it feels from sub-20 — good luck!