I "think" your Mixed Content is coming from the SOVRN ad in the right column. I've come across this on a couple of other sites already. It won't show up in the HTTPS checker, because it's only called into the browser once the SOVRN script has been executed. I think it's probably a tracking pixel, ie a 1 x 1 image pixel. You can confirm that by removing SOVRN, and seeing if the warning goes away.
The TLS warning looks like a false positive. Chrome says that "The connection to this site is encrypted and authenticated using TLS 1.2".
The tester on this page, for example, also says it's using TLS 1.2.
As far as the affiliate link back to SBI goes, you can have links out from your page to an Not Secure HTTP page. When someone clicks the link, they are leaving your site to go to anther one. Your connection with the visitor is broken, so there's no security issue with your page. When they get to the other page, their browser will say "Your connection to this site is not secure" or similar wording.