When your feeds are set to display full text, the feed outputs both the full content of your article and an excerpt, or summary. Depending on where/how you are viewing the feed, you may be seeing one or the other or both (in Mailchimp, for example, you can set your RSS merge tags to display either the full text or the excerpt–so if you are working there, make sure you are using the excerpt merge tag, not the full text/content merge tag).
If you are using the alternate feed, make sure that the feed you are checking is the new/alternate one, not the original.
In some cases, the excerpt may not display the way you are expecting if another plugin or code is also modifying it. If you can share a link to your RSS feed, I may be able to clarify what you are experiencing.
As for Blogger, this plugin merely modifies the RSS feed being output from WordPress. If you can set up Blogger to pull the feed information, then I assume you can syndicate the feed there, but that could be done with any feed, I expect.