Hello, sorry for answering so late (we have much different time zone I believe)
Well, first of all if you won't open the window your bird will never fly away

And with Ako... Well. Prepare for a long story ;P
I wanted to let him out on his own (I open the cage and walk away and he flies out) after like a week of having him. But he was so scared to go outside that he was staying in his cage and it was for like a week and no progress.
The cage comes with plastic perches and I really wanted to change them to wooden ones so I decided to do something kind of cruel to Ako. I took out the bottom of the cage and lifted up the top and just kind of pushed him out of his cage ;P
First he panicked, was flying arond the room and didn't know where to land. Finally he sit down on top of the cage, then 1 more round around the room and, surprisingly, back to his cage.
Next day when I opened the cage he came out with a bit of hesitation. But he wasn't tame. Was afraid of us, woudn't come near. But day by day he finally stepped on my shoulder

And then... I discovered parrot blog and forum ;p
Now he steps up on my arm (we're still working on stepping on my finger) and when I show him I put treats in cage he's not doing any problems with going inside.
About clipping the wings... It's your choise, but your parrot isn't a big one, right? So it can fly around the room easily i guess. If you clip the wings, he can still climb up to the window (parrots are good climbers when I look at Ako) and can get out eventually and be attacked or even fall down. Personally, I think I couldn't do such a harm to my Ako and clip his wings. But this is only my opinion - you have yours to make. And if your bird is extreamly bonded with you, I even saw on youtube people taking their parrots outside the house ^_^
Oh, 1 more thing. In the beginning I couldn't get him inside the cage - I was just catching him through the towel
But since you wrote that target training is going well, I think you shouldn't have problems with that (just let jojo enjoy a bit for staying out of the cage ;P). Just don't forget to show him first that you put in cage something he realy likes
PS. I'm sorry my answer is so long, but I just didn't know what to write and what not to write so I put everything here
All the best
Kath and Ako.