Trailer towing hookup questions

Im going to be towing with a 98 Dodge 1500 Sport. My car trailer is an 18' with a dove tail ramp on back. I would like to get my truck setup to the trailer correct so it drives and handles the best possible when towing my 66 Dart. This is an open, dual axle 7k trailer and it has electric brakes that work. Here are a few questions I have about towing hookup.
Should the trailer sit level, slightly up or slightly down for best towing? I have a 3.5" drop receiver and the top of the ball is 20.5". When I hook up the trailer on level ground the trailer front is 7" higher then the back of trailer just before dove tail. I'm thinking I need to go to at least a 5" drop?
Also a big concern is the tongue weight once loaded. I've seen different setups with scales built into the receiver or with the ball. Then I've talked to people that say use a bathroom scale. (don't think mine would go past 250 or 300 lbs) But what should be a correct tongue weight and how are you measuring it?
I would like to space the weight of the load to be evenly distributed on the trailer axle so that the tires do not get over worked/heated as I drive. Also how do you secure your car down once on the trailer? I've read some pull down on body which compresses the shocks and springs/torsion bars and others say just secure over the a-arms and rear end housing but let body move. What about the newer style wheel wrap tie downs?
Also how hard do you setup the brakes from the controller?
Would appreciate any advice and experience any of you can offer. Since I am just setting it up I would like to get it right the first time.
Thanks Rod