Getting my horse to lengthen trot..?

I am going to try to put this into words the best I can so bare with me. You need to work on collection with him to achieve both of what you are asking. When you ask him to trot pick up your reins, add the pressure one rein at a time, until he drops his head. As soon as he gives you give back. Remember to use your seat and legs to encourage forward motion. A horse really can't use their hind end with their head in the air so this will help encourage him to use his hind end which is the basics of collection. This will help you build on extending the trot and getting a collected lope. Sorry if this does not make a buch of sense. It is kind of hard to put into words, well at least for me it is. But I hope it helps and good luck.