Gents,
Feet entanglement is something I would like to discuss.
1. Is it always a no-call if a pass is thrown and the DB is clearly beat but is looking back playing the ball and his feet entangle with the WR?
2. Does time/score have anything to do if you would call DPI?
Never say "never", or "always", but I would suggest the key to your questions lies in the words chosen for NFHS 7-5-11-a; "Unavoidable", "simultaneous", "bona fide attempt", " to move toward, catch or bat the pass".
7-5-10-a & b advises it is interference, "when a player....interferes with an eligible opponents "opportunity" to move toward, catch or bat the pass". The language chosen for both rules point directly to intentional behavior specifically intended to prevent an opponent from doing something they are ENTITLED to do.
Aside from one player deliberately tripping an opponent, or in some way consciously and intentionally entangling an opponents feet, problematic contact with players feet is usually considered "incidental". As ALWAYS the deciding factor, between illegal and incidental, rests with the covering official, which only highlights the necessity of both positioning, focus and observation of the ENTIRE action.
As for allowing time remaining, or score, to affect your judgment. That's a REALLY dangerous road to start down, that is full of deep potholes.