the hood on this will fit most helmets, but some bulkier bike helmets may compromise the coverage. As far as weather protection, it will work great for those conditions (check the delta sv for max warmth/breathability) I would suggest looking at the Alpha SL, because it has pit-zips (key for high-output activities), and a storm hood that will work better with bulkier helmets, and is only $50 more.
http://www.backcountry.com/store/ARC0613/Arcteryx-Alpha-SL-Jacket-Womens.html

This coat will certainly keep in dry in any condition. But I'm more worried about durability in your case. Are you going to be doing construction or similar type work? If so, you may need a coat that's beefier. SL stands for superlight, and at 10oz, Arc'teryx use lighter denier fabric than say their "AR" line. If you care more about durability than weight, then I'd look at elsewhere, as you will have a lot more choices and in general other brands are cheaper than Arc'teryx. If you get something like mud on the jacket, you should be able to wipe it off easily.

I'd suggest looking at the Alpha LT jacket, just a tiny bit heavier, but with more durable face fabric, and backer, so all around, tougher.Other brands are cheaper, and less expensive (initially anyway, until it comes time to replace it quickly) Additionally, the Alpha LT will give better breathability than the SL. As for cleaning, throw this jacket in the wash with an outdoor soap, then dryer for 20 min on med heat. this is way better than wiping it off, and will add life to the water repellancy by removing dirt and oil. the heat from the dryer recharges the DWR

this is a hardshell, an extra light hardshell...if your going for something super druable, go for a goretex 3L jacket, also called goretex pro shell, but all gore tex materials are very durable...and if you get it here, theres a unconditional lifetime gaurentee that comes with it

Accoding to the sizing chart, conveniently linked from this very page, the sleeves are 75cm (29.5 in) long on the XS. Shells tend to be cut a little roomier in order to allow you to layer insulation underneath. Although I've never tested this particular jacket, I would assume it will be roomier than your standard fleece or softshell.

i would definitely go to www.google.com and type in"(insert number) inches to cm"it should give you a quick conversion

this hood will stay in place when you roll it up and zip the jacket, but it doesn't have a specific tab.