I charge whatever I can get! Rates also have to do with where you are, who you know, reputation, and what other offers you have on the table. That being said, here is what I would estimate each at:
-Website templates
I buy all of mine from themeforest for like $30. I don't see why anyone would do otherwise unless they needed something really custom. I don't like designing website templates, so I would charge $200/hr (a.k.a. I'll never do this)
-E-commerce websites
$75/hr
-Wordpress/Joomla themes
Again buy themes from themeforest cheap. Wordpress site maintenance and installation seems to go for $20-$50/hr around here.
-Some SEO from time to time
Experts will charge as much as $100/hr, basic stuff like putting meta tags in or running a google ads campaign could go as low as $20/hr
-Adding responsiveness to websites
Nowadays this often means starting from scratch. I try to quote for the whole project on something like this, but to give you an idea I would say around $40 an hour (give or take 20)
-Website designs
Same as above. ~$40
-Dynamic websites
I'm assuming this means webapp? I charge around $85/hr for webapps. Usually using angular. I also have started putting the webapps through cordova/phonegap, which is an easy upsell.
And to icpmacdo's point:
-remote backend development
Same as webapps, around $85/hr seems to be the magic number. This is VERY dependant on who you know and where they are located.
Note: All of my rates may seem high for people who find projects online, not in person. They may seem low for experts in their given field. Also, I find the larger the company, the higher the rate. For backend work you could probably get double that if you are an expert in large corporation java work.