Hard to answer as there are so many variables.
Breaking the project down and running a few smaller test prints usually helps.
What you will be suprised by is how much longer it all takes than you expect.
Once youve run a few test prints of your design and experimented with the materials it starts to get easier and more predictable and repeatable.
Read up on the materials you are thinking of using and look at what others have done with them and how they have set up the printer to do it.
1, This can be variable depending on what you are printing and wastage in failed prints and support material. If your wanting to know how much filament you need. The best way is to order 5 or 10meters and do a few test prints of your intended project an go from there. You will also find out what materials are best for your project by carrying out test prints.
2, The ultimaker takes 2.85mm. Theres some that say 3mm will fit. But with the rough texture of the wood filaments Id not take the risk. Some filaments advertised as 3mm turn out to be 2.85mm. You have to talk to the suppliers to make sure.
3, This all depends on the project. Glue works well but is material dependent. Super glue seems to work with a lot of materials. But test there effects. Acetone works well with ABS, it just melts the plastic a little and when you push the parts together they stick. Perfectly safe. Location tabs or plugs and sockets help line things up. But there are so many factors involved they cant be summerised here. Have a look at how others have joined similar parts on repositories like thingiverse.com.
4, again design and material dependent. You will know after a few test prints with the material and design if you can get away with filling the bed and leaving the job to print. One consideration is time.
If youve got 5 objects to print that take an hour each. They will take 5 hours if you group them or 5 lots of one hour with a little prep between prints. What suits your schedule best? If they have post print finishing to be carried out doing them individually means you could be finishing off one while the next is printing.
5, Yes, you can have 100% infill which gives you a solid structure. But it is a waste of filament on large prints. Again it depends on what you are doing and material dependent. Its useful for small or thin parts for strength. For larger prints that honeycombe or gridded infill is incredibly strong. Also a solid 100% infill may be impossible to print on larger objects due to shrinkage and warping due to heat variations in the printed object. Again design and material dependent the only way to find out for your particular design is to run a test.
Gordon