General answers, no doubt someone will get more specific on things.
1) Military ships: generally the wisdom is that missile ships are stronger tactically, beam ships are stronger strategically. Meaning that missiles are great in a fight but it's really tough to carry around a lot of extra missiles. For your first ships, I'd recommend you go for missile ships.
2) PDCs are a good choice, certainly, and for missile launchers, the PDC versions are quicker to reload. Really only good for big investment planets. Ships are a good choice because they can go where the trouble is.
3) That very much depends on tech level, and there's lots (and lots. And lots) of discussions about missiles. More than an optimum range for a particular type of missile, you should look at your techs and make sure that you can a) spot a ship, b) fire control reaches that far, and c) missile reaches that far. Design your sensors, fire control, and missiles to match those ranges (you can add a bit of padding on sensors and fire control to allow for growth in missile designs) and then make your missile as fast as it can be to get as far as you need with the amount of warhead you want. If you have any room leftover, agility's good. If your reeeeallly need a number to shoot for, 50m is doable with low tech, 100 is better with just a bit more tech, but don't be surprised to see people talking about missile with much bigger ranges than that.
4) Congrats, I'll give you a definite answer on this one! Yes, jump drives on scouts and survey. Those are your friends. The whole idea of the scout is to see what's on the other side before you commit the resources to something like a gate. Your scouts will (usually) be a couple of jumps ahead of your construction anyway. Jump drives for them are good. Depending on your play style, you can either make an all-in-one ship that does gravitational and geological surveys and has its own jump drive, or you could make one ship (grav survey, say) have a jump drive big enough to carry through the other geo survey ships, or you could make 1 ship as the jump tender and have both grav and geo with no jump drives. Up to you. I go with option 1, because a) I'm too lazy to keep track of which is which, and b) it only needs 1 shipyard tooled 1 way.