One post per page, with comments an older/newer-navigation

Hello!

I just set up my first WordPress Page, it works great and I really like it. I have a few question, though:
1) I want to display one post per page, as my posts are rather long and have a lot of pictures in them. Unfortunately, when I set the reading settings to 1 post per page (which works) I don’t have the comment section displayed; I have to click the post title to display the post, but then the navigation disappears. Is there a way to immediately display the newest post on the first page, with the comment section and navigation links to the newer/older posts?

2) (somehow related) In my menu I want to add a link to the my very first post. I did this using the permalink (url/?p=287), but then the visitors are not able to move forward to the newer posts, because the navigation links are missing.

3) I use a simple widget to page plugin to display my categories on the page, and I also have a menu with all my categories. I want both the menu and the links to refer to the first post of each category, also with comment section and navigation links visible. Is there a way to do this?

i don’t know if my questions are theme related or belong in this forum, sorry for that!

Best Regards,
Mischa