Do Jehovahs Witnesses believe Eccl. 10: 19 is literal or is limited in application in some way?
First, let's define the crowd you mean when you use the term "Jehovahs Witnesses". Do you speak of the R&F JW? Or do you speak of the JW hierarchy -- the JW Leadership, ie, GB?
The Leadership, including the GB, DEFINITELY believe money is the answer to everything. At the same time, they "preach" to the flock to "keep the eye simple" and ridicule anyone who "is determined to be rich". Of course, both of those examples are fluid. What is "simple? And what is "rich"?
I believe that the average JW today has a greater concern about financial stability than their peers from decades ago. The JW today DOES NOT count on Armageddon "fixing" all their problems. Instead, the average JW is carrying on in life just like the average "worldly" person. For example, husband & wife both have jobs. Ten or twenty years ago that didn't apply to higher education, but today even many of the average JWs are going to college or at least some kind of higher education (trade school, etc). Lots of the men are in union construction trades and many of the women or in nursing. All the young JW couples that I know of are traveling extensively -- seeing the sites of the US, going on cruises, and even international trips are quite common.
They all have come to realize that "money is the answer for [almost] everything". I added the "almost" because we all know "money doesn't buy happiness". Of course, it's a helluva lot better being rich and unhappy than broke and unhappy!