Way too tough for me I think but I have a few and will stumble on a while. To help, could you confirm if the crowded cells actually share common letters (I assume not as a rule from the 3D check) and is there more than one crowded cell in some answers? Don’t answer if it gives too much away! Thanks.
Ethik - I find it helps to list the alphabet down and place a 1 to the right of the A, 2 to the right of the B etc and then put a 27 to the left of the A, 28 to the left of the B etc. When you have solved a clue and have the extra word and the solution word just take the first letters of both and add them together - so (e.g.) N + P = 14 + 16 = 30 and 30 on the left column = D. Hope this helps!