Hard to beat Yuasa. There is a good reason they are spendy. I have one made in July 2004 still going at around 75%. A tender is your friend in the off season.
Paco
Treat yourself to a new CTEK charger and keep the manual charger as a back up. They are handy when you need to use a dumb charger to put a base charge into a really flat battery when a smart charger wont do it.
Paco
It depends on the signal strength of your stations. With a strong signal even a bare piece of copper wire works. The further the station and the weaker the signal the bigger, better, higher you need the antennae to be. Don't forget free streaming services if you have internet.
Paco
The plastic cap is fine if you do your own oil changes and know not to over tighten it. It seals on the O ring so it doesnt need force. There is also a retaining clip so that it doesnt back off once installed. If you let the loober goober at SpeedyLube do it you will not be happy afterwards. I...
I wouldnt think one tooth difference on the front sprocket would be a large increase in wear. If you were dropping down to a 13 or 14 that would probably cause a noticeable difference over time.
Paco