That pace is fine as those are reasonable miles to be doing. It'll pick up.
For rain gear personally I like MTB shorts. They tend to repel water/wind pretty easily. A light water resistant jacket is all I wear specifically for rain. If it rains, you'll get wet, no point trying to really fight that too much, just stay dry enough to be comfortable. You don't need full fenders imo (although they will protect you and the bike better) - you can get by with just something simple (seat post mounted) to stop the skunk stripe.
I have a 9-10 mi commute each way and for tools, etc. all I carry is a spare tube, pump, patch kit and levers. But there at least 2 bike shops on my route if things get really bad.