Hi

At 16 weeks, he's still learning and everyone, and everything is so exciting! Start back to basics with his recall and practice at home, or if doing so outside, make sure its quiet with no distractions (dogs or people).

Each time you recall him, reward and then send away to play again. Don't call him and put him back on his lead as it will be quickly associated that recall=hometime=end of play. To really get his attention, you may need to call out in a silly voice, do a dance, whatever it takes to get his attention back to you.

You may want to look into getting a 'long line' (can get these at pet shops) as this is a long lead that's more controllable than an extendable lead, and better for recall training than a standard lead. Plus it will be some protection to your pup on the off chance he decides to cross a road, or runs up to a dog that isn't so friendly with others. Recall training and good off-lead walking is one of the aspects that can take a while in some dogs so you will really need to persevere before letting him back off the lead. Remember age is a strong factor in this as well as breed. Terriers are fun little dogs, but they can be independant and dare I say it, stubborn!

Do you go to a training class? If not, you may want to look into a good puppy/adolescent class. Not so much for the training if you're managing otherwise (but this helps), but more for the controlled environment to teach puppies these skills. In the park when there is too much going on, not all youngsters will want to learn and for owners, its difficult to catch their attention. A puppy class should only have a handful of other dogs and its easier to learn this way.

As for the pooing in the house, how often does he do this? If he's generally clean, again this is an age thing. Some pups will 'forget' their housetraining and may have the odd accident. Again, go back to basics-let him out after sleep, play, feeding...and reward! He will get the hang of it!

Good Luck!