Some answers:
(1) To adjust midi volume, you could adjust the main volume, or the velocity. This is done via the key editor. In an orchestral contest, the mod wheel is often mapped as a volume control, but it’s a bit awkward to use unless the mod wheel performance was part of the original performance. You also have the option of using automation, or converting the midi to audio, then using audio tools.
(4) Recording drums with a MIDI keyboard, one often encounters the issue of drum maps. Sometimes it’s good to remap the drums so that the layout of drums on the keyboard if favorable to making natural finger motions resemble natural drum stick motions. For example, mapping adjacent keys to the same (or similar drums) when attempting to produce a flam. It’s well worth the trouble to get a pair of drumsticks and do a little fake drumming using a phone book for a snare and tapping your foot on an imaginary bass drum. Even a few minutes of this will give you a sense of reality when it comes to building drum parts. Also, unless your timing is excellent, keyboard-entered drum tracks can come out too sloppy to be useful.
Recording violin on a MIDI keyboard is easier, especially since it’s usually a one-handed operation playing single notes. It gets more complicated when you introduce the mod wheel as a volume control. This style of playing is quite different from playing normal piano parts. There are a lot of youtube demonstrations of this by guys who do film scores. I’m impressed by how often they can nail it on the first take. I think it’s safe to say that it’s a special skill, which might affect the direction of your development as a keyboardist.
Other than that, try to play pieces that you enjoy so you won’t dread and avoid playing. How many Hannon exercises can anyone do without zoning out? You should also select pieces that develop a particular skill that you’d like to have, such as playing octaves in the left hand, or trills in the right hand. It’s good that you have a teacher. That should prevent you from falling into bad habits.
(5) As with all musical instruments, you can expect to go through a trading-up process. Very cheap instruments often mask what the performer is trying to play, while also masking mistakes. Obviously, that would slow you down. That said, you need to go and try a few out. The reaction of the keys themselves is important. How stiff are they? Are the weighted or semi-weighted? Does it feel to you like you’re hammering nails with your fingertips, or that your hands are wading through a sea of mush? You would know when you personally audition keyboards.
If you are going for just a MIDI controller, then your money will go much farther if you avoid synthesizers. Why pay most of your money for hardware sound modules if you’re going to run softsynths anyway?
(6) Recording with pedal effects is not really different than recording clean. Just get the gain staging right in any case. In some cases, that could mean some sort of preamp or di box. (Depends on how well your audio interface deals with direct injection.) It would get tricky if you wanted to add pedal effects as an outboard effect. Recording with the pedal effect is fine unless you think you’ll want to change the effect in the future. In that case, you might want to record it clean and use inserts or sends later on. Obviously, that’s a complication that can slow down your work. I don’t use guitar rig, but it looks pretty decent and has a great reputation, so I imagine it’s not that tall an order.
(7) yes, you can have other windows open when using Cubase. However, you are right to fear viruses. Also, most games will put a strain on system resources. If you have a game loaded and then decide that you want to grab an instrument and play this great idea you just had (without quitting the game) then expect Cubase to produce a lot of crackles and drop outs. This won’t happen if you quit the game first.
Now, when you add virus protection software to your system, it will always be running in the background, siphoning off resources that could have gone to Cubase. This is usually tolerable, depending on the anti-virus program and how much power your machine has to begin with.
(9) It depends on you. There are people out there still running Cubase 3, or Cubase 5. Like buying a new instrument, it depends on what limitations are bothering you. There could be a bug you can’t live with, or a new feature that you lust for. Then you’d be motivated to upgrade. I like to keep up to date with every new release, waiting a few weeks for the worst issues to emerge and be addressed before pulling the trigger. There are also special prices available from time to time. Study the history of when such sales typically occur. Watch your e-mail notifications. It can save you a lot of money.
It costs a lot less to go from Cubase 9.5 to Cubase 10 than to just buy Cubase 10. Likewise, going from 10 to 11. I’m not so sure about upgrading from Cubase 4 to Cubase 10. I believe it’s like starting over.
(10) I don’t know why you experience more latency with orchestral parts. Certainly, those instruments tend to have slower attack envelopes by their nature. Does it happen with timpani or glockenspiel?