the logo must link to the frontpage
AFAIK there is no SEO benefit of doing this, as long as there is some other link elsewhere on the page that links to the homepage.
However, it is common convention to do so and consequently users often expect this. So it can improve useability, but I don't think this has any SEO benefit specifically.
every page with the 150 block of links should link to the /sitemap
If I have understood correctly, I don't think this just applies to "page[s] with 150 block of links" (that is irrelevant IMO), but to every page. Including a link to the sitemap on every page could benefit SEO by simply improving the internal linking of the site and hence its ability to get spidered by the search engines. This can also improve usability in case the user gets lost - a sitemap link is often found in the page footer (common convention).
A smaller site that already has good internal links probably wouldn't benefit so much SEO-wise from including a link to the sitemap, but there could still be a usability benefit.
sitemap should link to every single page, not simply to the blocks of 150 links [COMMENT]
I don't think this would necessarily provide any SEO benefit in your case. What the SEO "guru" might be trying to avoid is deeply nested links, where pages are nested 5 or 6 levels deep. There is potentially a limit to how deep the SE spider will go. But I don't think that applies in your case (homepage -> sitemap -> carportal -> car). And it is probably best to avoid 1000's of links on a single HTML (sitemap) page (this is not an XML sitemap). On an HTML sitemap it is perfectly acceptable to categorise the links, which is what you seem to be doing. An HTML sitemap is, after all, as much as (if not more so) a benefit to your users than SEO.
YouTube video by Matt Cutts:
Is it still important to offer a site map to users?