The truth is, most of what you will find out about a girl or guy, is what is discussed on the dates. If you’re nervous about a certain dress code, see for your self how she/he dresses on the date. If you’re curious about her past, then start up a conversation about schools and camps the both of you attended. A lot can be determined by the first or second date, depending on how aggressive or outgoing you both are. The shidduch scene is a tough one, and I feel for those who have to endure it, especially when it takes a long while to find your besherit, and having to turn someone down, or be rejected yourself, but don’t despair, there is someone out there for you. I can’t sympathize completely with you, or others who have to deal with all this (Hubby was my first date), but I have people who I am very close to going through it. Some have been out with over 100 men (not exaggerating), but they DID find their besherit, they have children together and are very happy.
You also have to realize that many lies get spread around about people because of what someone supposedly “heard.” Also, there may be things you don’t find out till you are engaged or married. There is no 100% fool proof way of knowing someone completely before you marry, or knowing if the marriage is going to last. You just have to have faith in Hashem, and that He is guiding you in the right direction.