I've been to them all. So for Tokyo, I'd recommend at least 3 days, possibly 4. Both parks are great and you'll want to do them in great depth. Also keep in mind that they get very very crowded. If you go on an even average day, you will only get a few attractions in. I would highly recommend booking to go during a slow time of year. Also, unlike other parks, in Tokyo guests line up super early, and then when the park opens they take all the Fast Passes. So you need to plan to be there a good hour before park opening.
For hotels, the Disney hotels are quite expensive but there are a number of good neighbour hotels that are going to be better. Compare those to hotels in Tokyo. I'd suggest 4 days at Disney and then move to a hotel in Tokyo for the next several nights to see the city.
For Hong Kong, think of it as Disneyland light. It's small, and without a lot of attractions. One day would be plenty. However Hong Kong itself is another wonderful city. I was very pleasantly surprised by it. I would suggest staying in the city. Then you can just take the subway to Disneyland for a day. Maybe go to Hong Kong before Tokyo... otherwise you'll be really disappointed with DLHK.