
Sounds like you are having fun!!
At 7 months old, your lad is a teenager - and selective deafness (espesh with recalls) is very common. Everything else is just too interesting! The yo-yo recalls you have been doing are excellent, keep doing them - but I'd restrict it to a time when you can be sure there won't be anything distracting for him - like joggers! It's important with a recall to build up to big distractions; for example, a dog that will happily come in an empty field probably won't come if that field is full of rabbits :)
When there will be people around, I would have him on a lead - you can start on a 6ft till he's more reliable, then work up; i start on a 6ft lead, then a long flexi, then a 30ft longline, 50ft longline, and finally a 100ft longline (though I'm not there yet - those darned rabbits!). Hopefully your guy will be reliable enough with training so you won't need the 50ft or 100ft - they are a royal pain to work with!
Start by calling him when he's coming to you - I have found that it's most effective if you say "dog, come!" or whatever your word is. I found "come" works well because it starts with a hard sound - and it's easier to get across firmly if you need to say it louder. One very imjportant thing - *never* use your recall word if there is *any* chance he will ignore you, unless you are sure you can correct him. This will only teach him that he can ignore you and get away with it - keep running around and sniffing stuff - and it will set your trainnig back. I've made that mistake myself with both my dogs, and it does make it that much harder to get a reliable recall- even when they are very reliable on lead, I find (espesh with my dobe) that once he's off, he remembers he can ignore me and will do it.
The joggers - keep him on lead if there's one around (or likely to be), and when they get near, start giving him little treats - soon he should start associating the joggers with great stuff, and start looking to you. If he stays on the ground when one goes by, give him loads of praise - the whole shabang, daft high happy voice, jackpot reward (loads of great stuff like hotdog), the works. He should soon get the message!
Once you've got him reliable on a regular lead, you can move on to a longer one - some people don't bother with a flexi, but I like to; the whole retracting lead thing makes it a bit easier while you keep working on that recall. When he's reliable on the longer lead, go a bit longer - if you can get a light but strong longline, so much the better - it will put less drag on the collar as you are walking, giving the suggestion of freedom to him. He might become a little less reliable then, but that's fine - more opportunities to work on it, and remind him he must come back.
For the actual training, here's what I do; in the first stages, I click and treat for any time the dog comes after I've called it, doesn't matter how long it takes (well, up to a few minutes anyhoo - I'm impatient!). You don't have to use a clicker, but a uzz-word helps - like "good boy", "bingo!", anything like that - anything that will make his returning to you stand out as the thing you want.
Then I start upping the criteria - I click and treat for returns within a set time, not after. As an example; right now, my dobe is on a 10-second recall. If he returns within the 10 seconds, clikc/treat. At the 10-second mark, I (gently) pull on his flexi until he comes back. When he's in front of me, I ask him to sit, and say "good", in a calm, quiet voice - he knows that him returning is what I want, but he also knows the reward isn't amazing - makes the click/treat stand out that much more.
In a week, he'll be on an 8 second recall - same thing. Return in 8 secs, c/t. No return, slight pull till he does. A week later, it'll be 6 seconds and so on, till I'm only rewarding the turn-on-his-heels recalls. Then it'll be the turn-on-his-heels and *run* back recalls. That's called shaping; molding the behaviour you have into the behaviour you want. Be careful - just this morning I made the mistake of clicking as my other dog turned towards me, only to watch her get distracted again and investigate something. I clicked her for looking at me, not coming back; make sure you breward only when you're sure he will come back, same as when you use your magic recall word. Be sure to always use the same word, too - he'll associate it with good things happening, and every time good things happen, the power of that word will increase.
How long your boy takes I couldn't tell you; I'm working with two very, very independant dogs, so it's taking a while - not to mention the immense hurdles of rabbit and squirrel temptation.
Good luck, sorry that was so long! One method doesn't work for every dog, of course; this is one I've developed through talking to a number of different people, owning different dogs - dobes, rotts (my other dog is a rott X), french bulldogs, weims, all sorts!
One last thing; I recommend a book called Don't Shoot the Dog, by Karen Pryor - it explains all about learning theory in all mammals (ourselves included), and is very useful when working with any dog.