1) Lima - I personally don't think so....with so much more to see, I'd spend it elsewhere.
2) - not sure as we only went as far as Puno (about an hour from Juliaca)
3) - Went to Uros...frankly, it touristy...you can go to several Uros islands as they are all right next to eachother. You go on the island, meet some of the people, they'll show you their home, and they you buy some trinkets from them.....although touristy - I loved it! Uros is like a 10 minute boat ride from Casa Andina Private Collection (where we stayed) Nice property right on the lake. We also took a boat to Taquile, hiked the island and then had lunch with a local family. We were on the lake all day....loved it.
4)not sure

Also - regarding your time at MP.....I would also hike to the Sun Gate...it's where people come through when they hike the Inca Trail.

Have a great time!

4) Yes, there are one way tours available from Copacabana to Tiwanaku/La Paz. An example of one you can find here: http://www.fertur-travel.com/bolivia-tours/extension-puno-la-paz-bolivia-3-days-2-nights. Fertur is a highly recommended, reliable operator.

Happy travels,
Danielle - Latin America For Less

The link that Latin America for Less posted looks like the first day is the Transturin Catamaran one day tour (Puno to Isla del Sol to La Paz), cost was around $215 plus taxes last year. This goes through Copacabana but doesn't stop in Tiwanaku.

Then they put you up in a hotel in La Paz for two nights and do a round trip tour to Tiwanaku (probably the Turisbus day tour out of Hotel Rosario).

I have not run across a tour that connects Copacabana and Tiwanaku, since they are on different routes between La Paz and the border. You might contact a Bolivian travel agent, have a look at Crillon Tours page for La Paz.

http://www.titicaca.com/English/ingPRGLapaz.html

On August 8 is there an earlier flight? I don't know if you will make the border before it closes with a 3pm flight. Most of the tourist busses leave Puno in the morning.