Vertical and lateral flextion
I'd get his body collected and the head will collect with it. I don't worry to much about my colts head as long as his back is round he's pushing from the back and lifting his shoulders. Once I had that his head was low but collected. I haven't once used draw reins, martingales or any other mechanical devices.
Have you tried using draw reins or a training fork? They help send the message to the horse with out tugging on their mouth a ton!
I think it's best to get an instructor. There is a thin line of true collection. Many people teach their horses to avoid collection by going behind the vertical.
Just collecting your horses head isnt correct or true collection. You have to start with impulsion first. There is a pyramid of things you need with collection at the top. Its a complex subject so you should read a book about it so that you do not go about it incorrectly and risk hurting your horse or training them to do incorrect things
I have contact. I keep my outside rein with steady pressure/contact and gently massage my inside rein (like you're playing piano almost. Move your fingers gently.) my horse will bring her head down to this if I release right away. One thing I've learned not to do is see saw your horses head into the frame, it isn't proper. I'd also seek help of an instructor as there are different techniques