My site runs on a dedicated server and and has Wordpress in a subfolder.
I have my mainsite which is not wordpress and that has a sitemap - for example example.com/sitemap.xml ... that sitemap is updated by a php program and is auto submitted to google and bing. This sitemap only contains pages that are in the root of my domain and has approx 1000 entries.
I have a robots.txt in the domain root containing for example Sitemap: http://www.example.com/sitemap.xml
I now also have Wordpress installed in a subfolder - for example example.com/news/
I also have the free Yoast SEO plugin installed but currently have xml sitemap functionality disabled.
I have several related questions.
1) What is the best way for me to have multiple sitemaps - the mainsite one and one or more for the wordpress part of the site? My wordpress articles are mainly news articles but I am not accepted into Google News yet.
2) Should I just enable Yoast sitemaps or should I use a different sitemap plugin such as Google XML Sitemaps or even some other sitemap plugin (I looked at Better WordPress Google XML Sitemaps but that currently says Compatible up to: 4.4.7 Last Updated: 1 year ago) - I am on Wordpress 4.7.2
3) Do I replace the line in my current robot.txt with a sitemapindex
4) Should the sitemaps have different names - for example sitemap1.xml and sitemap2.xml
Any other considerations would be appreciated.