I understand, I am the same way with my bike. But for a bike THAT expensive, I'd get a cheapo cable lock - one of those 6 foot long $25 jobs, and leave it in your desk JUST in case. You never know. Actually I have one of those and carry it in my backpack. I lock up at work/school whatever so I just leave a heavy duty chain there. The light weight lock is just insurance against it walking away in low threat settings or if I need to duck in a store for a minute.

I'd also consider leaving the heavier tools in your desk; when I flat during a commute I just hop on the train and fix stuff at work/home anyway. I used to leave my seatbag in my desk but now I carry it because in our present building people have been known to waltz in and go through desks (don't ask - it ain't the Waldorf Astoria!!)

for your mtb, the slicks are the best mod; you could also try lightening it by taking off any extra stuff. some folks remove the two smaller chainrings and just go with the 46t or what your big ring is - personally I think those weight savings are minimal. You could try getting bigger chainrings or get a 'corncob' (closely spaced ratio cassette with smaller cogs, like on a road racing bike), another popular mod for mtb use on a street. The weight is tough to change though....it is what it is.

I used to mash bigger gears when I commuted on a road bike; the last few years I've been on a SS cruiser, an English three speed and now a full rigid mtb. In each of those cases, with the extra weight I was happy to have lower gears and did the sit & spin up over the bridge.