Questions about date stamp, post updates, permalinks and SEO

Hello
I’ve searched the forums here and looked at other sites to try and find some clear answers for these questions, but honestly, I’m just getting confused. I really hope someone can give me a hand.

My blog (http://www.iconicalternatives.com/) consists of posts that I update every 4 to 6 weeks on average to keep the content fresh. I am using the free version of the ColorMag from ThemeGrill for my site (and I have already posted some of these questions specific to their theme on their forum). I am at a basic level when it comes to editing CSS or php, but I can manage some simple tasks. I have the following questions:

1. Since I update my posts regularly, is it possible to display (on both the Homepage and each post) the date of the most recent post update instead of the date of the original publication? Can you please provide instructions?

2. Does anyone know if changing to the most recent update date will impact SEO (luckily I have some posts that are already ranked highly)? I do not want to change the actual “date of publication” for each post – I believe this would negatively impact SEO by changing the URL (I use /date/postname so the link would break), as well as mess up what is displayed on the Home page (most recent posts). Additionally, I think using the date of the most recent update would help SEO, since (as I understand) more recent content is ranked higher.

3. Ideally, I would like the SERP to either not show the date of publication or show the date of the most recent update. As a basic workaround in the short term, I’m adding the text “Updated on Month Day, Year” to the start of the meta description/snippet for each post once I update it to inform visitors. But does anyone know if there is a simple way (without digging into Javascript) to hide the post publication date or display the most recent update date on the SERP?

4. Regarding permalink structure: I am seriously considering changing from /date/postname to just /postname/; I’ve read many posts on SEO best practices that recommend this format for a variety of reasons. I currently have 70 posts and some of them are ranking very highly in search results so I don’t want to mess that up by changing the permalink structure. But I also think that if there was a time to make the change it’s now. The questions I have:

a) Is there a way to do a massive 301 redirect for all posts that will not negatively impact SEO too much?

b) If not, is advisable to manually use a 301 redirect for each post? I would probably use a plugin like “Redirection”.

c) Once I have changed the permalink structure, should I update the xml site map and resubmit it to the search engines?

d) Is there anything else to consider that I haven’t thought of re: changing permalink structure?

I completely understand I’m asking for A LOT of answers in this post. But I really have been searching hard for the last 2 weeks to find clear answers and (as I said) I’m still not clear on the best strategy for moving forward. A big thanks in advance to those of you who can offer some help. If I can put together a clear plan for doing all this with your input, I would be more than happy to write up a “How I did it” post for future reference to give back to the community here.

All the best!
John

The blog I need help with is http://www.iconicalternatives.com.