You said your window was 34 inches wide but you didn't say the length. In any case I wouldn't use an extra wide one. I'd stick to one 1 to 1 1/2 inch diameter. As for the extention it can be what you want it to be. On a small window I would put the finials an inch or so past the molding.

Pinch pleats are relatively easy to make. First you need a drapery tape to back your pleats. Cut off the selvidges. On the wrong side put the tape near the top edge, leave the hem width without the tape, and fold about 1/2 inch of the material over the tape and sew and again leave the hem width--1 inch hem leave 1 1/2 inches. Sew the side hems going over the tape. The tape should now go to the side of the drape, making it stiff all across the top.

Now fold the tape down so it is encased in the material and sew across.

Now comes the figuring part--you need 1 1/2 to 2 inches on each end. Measure the curtain across and subtract the amount left for both ends. This is the amount you have to pleat.

Each pleat will take 1 inch, so if you have 3 pleats it will take 3 inches. 2 pleats take 2 inches, but you won't have the fullness. Then leave up to 3 inches plain and then another pleat. Don't forget you have to add another pleat on the other end.

Fullness comes with how many pleats you make and the distance left between pleats. You may have to fudge the distance between to get all the pleats in.

Once you've figured out how many pleats you need then measure and pin. The pleats will just be a 3 inch--or whatever--hoop. Adjust the space between if you have to, until you have it right.

Now sew the pleat hoop from top to bottom of the tape. Take the hoop and finger press or iron in the 1/2 inch pleats. Sew the three pleats together at the bottom of the tape, and the pinch pleats are done.

I'll check in later if you have any questions

Now fold the tape down so it is encased in the material and PRESS. If you sew it down there will be no place to insert hooks

Most drapery fabric doesn't require it. If it has good body you don't need it. If it will fall nicely that is all you want. Personally I have never used interlining and have always used drapery fabric. Drapery fabric is usually wider than dress fabric. Some of it even comes in widths you can use for the length.

You could use buckram for the header, but why not pleater tape. It is very stiff and stays that way when it is washed or dry cleaned. They do have some that you pull strings to pleat the material or the plain kind that you use for pinch pleats. It saves all the cutting.

If you could give me the size of your windows including how much you want the drapes to go past the windows on top. What material you are making them from and the width, and how full you want them, then I can tell you just how to make them.