I also recommend the kong wobbler, or freezing his meals in a kong (or multiple kongs of different sizes-this is what I do for my younger dog). Also, the place command is a good one! I use "on your mat" or "in your bed". So handy! Also, if you use "on your mat" this can be used anywhere-visiting people, camping, etc ec, just bring him a mat, towel, something to mentally "tether" him to.
Alternately, you can toss him his kibble one at a time. Time consuming, but good if you're reading, doing homework, etc.
And there are toys you can get where they take things out of stuff, or put blocks in and get treats as a reward.
Keep teaching him tricks too...keep his mind busy. Anything you can think of! And start putting tricks together in sequences.
Also, you may have to consider just getting up earlier in the morning to exercise him. When my (now geriatric) male was younger, he needed about SIX HOURS of running EVERY day (not a border collie, he's a Ridgeback/lab cross). I used to get up at 3:30 or 4 in the morning and take him out. Rollerblading or biking with them is an excellent way to tire them out, although you'd need to wait a little longer for those until his bones and joints are done developing.