Hello Alfredo,
Series I electronics do not really have a 'flat position, other than for Q switches I guess. What you have is the following : 2 volume controls, 2 tone filters, 1 for each pickup, and 2 'Q' switches, also 1 per pickup & 1 pickup selector switch. The 'Q' switches are flat when they are up, I believe, and give you a 6 db boost in the middle position and a 9 db boost in the bottom position ( hope I don't have this reversed). The filter knobs operate between 350hz and 6000, cutting all frequencies above the chosen setting; if the knob is rolled all the way forward, everything is coming through, if it's all the way back nothing over 350 goes through; most folks use a setting somewhere in the middle; this gives you a much wider range of tonal control than a regular bass/treble set-up.
For the strings, I suggest you contact your local dealer who should be easily able to look up which manufacturers make short scale sets, and can order you some. I'd also suggest looking up some of the websites. I think D'addario makes a short scale XL set, not sure about DR.
Good luck, and congratulations on your new Alembic