17miles each way is a fair old whack, sounds like you're doing great to me. When I started cycling I was 245, and could hardly go 2 miles, took me ages to get up to those levels.
Don't worry about people going faster than you, there's always someone faster, and doing those miles the numbers passing you will magically reduce.
Cracks, especially long parallel ones are a real pain. The advantage of commuting is you get to know all of the perils, and can plan your line most of the time, I even know where potholes are in the fog on my morning route, and apologise to the bike when I hit one I knew was there. Tyres can make a big difference, I swear by Michelin Pro4's, there will be many other opinions though :-)
It's worth learning how to keep your bike running in tip top form, most jobs are pretty straight forward. A clean and silent bike always feels quicker.
Me I mickle the chain most days, my own method, run it thru a couple of baby wipes, dry off with paper towel, maybe clean between each link if it's really bad (easier with an 1/8th chain) got it down to a fine art now. Likewise wipe the chain rings and cassette, I run a cloth between each cog in the stack, simply put it in and the back and forth motion will spin the cassette round. Keep the derailleur and front mech clean.
Take your wheels off, hold the axle and spin them, do you feel anything, is there any play in the axle? Could well be time to repack the bearings, simple job, just you tube a video. Although it may well be worth getting new wheels with sealed bearings, mine are currently on 50k miles maintenance free.
Check the bottom bracket, I've had mine so I can hardly turn them by hand, but hadn't really noticed when riding.
Keep at it and and you'll soon have the endurance, and possibly even the need to ride each way every day (I know my body complains to me if I miss an opportunity)
