Putting food items in the mouth without making sure they go on down, can smother your snake, as the breathing hole is in the bottom of his mouth.
If this were my snake, I would try getting bait store minnows or Rosey reds, and freeze them. I suggest this because bait store minnows have a very strong scent, and roseys come second... while guppies do not have as much scent. I had 20 T sirtalis babies a few years ago, and the ones that were picky eaters would not eat worms or guppies.
After the minnows or roseys have been frozen for 24 hours, take one out and thaw it in warm water. When it is flexible and not overly cold to touch, take it out and gently blot it on a paper towel. Then... ewww!
... take an old pair of scissors and cut it into pieces that are a suitable size for a very small snake. Make sure the spine and rib bones are not poking out of the pieces. Save the guts seperately.
Get something that is totally flat, like the lid of a margarine tub. Using the "guts", mix the fluid from the guts with a little cold water, and sprinkle a little of the scented water on the lid so the fish will stay moist and have a stronger odor.
Lay the lid in front of the baby, but not too close. His tongue should start waving in the air as he catches the scent.
I have rarely failed to get small babies to eat in this way.