Your question: is David Crouch b. 1736 d. 1818 the son of Richard and Thankful (Frink) Crouch. I would say no.There is a will and inventory of Richard's estate which I assume mentions his heirs which I believe is the source of Richard's children list. Sorry I don't have the will. Anyway my children list has only Thomas F (my ancestor), Christopher and Elizabeth Culver.
We do have many David's and Richards in the line. The names are repeated so often it makes the whole line confusing.I found a line recently on the world connect project of Rootsweb which seemed well researched.Good luck.