Automation control & drum pads...

yes, it can be done.  a lot of people use controllers like the behringer BCF2000, presonus faderport, mackie control pro, etc.

but you can also use a keyboard if it has knobs or sliders that you can use to assign functions in sonar. 

use ACT to learn the MIDI functions of the controller.  I have never used it myself, so I can't help a lot there but there is information in the help files on how to use ACT.

as for #2 - I'm not sure what you mean by "control them from outside the program"  are you wanting to know if you can trigger an audio loop using MIDI?  if so, then yes, dropzone used to come with SHS, but I don't know if it still does.  it can trigger audio loops based on MIDI inputs.  other than using dropzone if you don't have it, then you'd have to find a sampler to use.  there may be some free ones on kvraudio.com I don't know.

You can use any MIDI-capable device to trigger any soft synth. I sometimes use my SR-16 drum machine, or the keys on my MIDI keyboard, or my brother's electronic drum kit to input MIDI data.