John Bolton was only ambassador to the United Nations under George Bush because Bush made him a recess appointment when his fellow Republicans considered him unsuitable for the post.
As per Wikipedia, Bolton is currently a senior fellow at the American Enterprise Institute, a senior advisor for Freedom Capital Investment Management, a Fox News commentator, and counsel to the Washington, D.C. law firm Kirkland and Ellis. He has been involved with the Institute of East-West Dynamics, the NRA, the U.S, Commission on International Religious Freedom, the Project for a New American Century, the Jewish Institute for National Security of America, the Committee for Peace and Security in the Gulf, the Council for National Policy, and the Gatestone Institute where he serves as Chairman.
For those familiar with these organizations, you cannot get much further right. If anyone in Trump's organization makes the case for war with either Iran or North Korea, it will be John Bolton. This guy is absolutely dangerous.
The Iran Nuclear deal will be the first thing they will scuttle.
I could use some four letter expletives to describe my opinion of John Bolton but will just leave it at that.
You mentioned a number of Bolton's nefarious connections in your post above.
This morning, decided to do more research on the Gatestone Institute, and came across a couple of very disturbing articles:
1) The March, 2018 article in The Intercept (cited below) lists several of the crazier ideas published by the Institute. The article also mentions the link between the heiress of the Sears, Roebuck fortune and the Institute, as well as the connections to Rebekah Mercer (the financier of Breitbart). The Gatestone website has not only influenced U.S. politics, but also attempted to influence recent European elections in France, the Netherlands, Austria, and Germany. The site has promoted far-right, anti-Muslim populists running for office across the continent. In Germany, politicians from Alternative for Germany, or AfD, the rabidly anti-immigrant far-right party, regularly shared Gatestone articles on Facebook and Twitter during the election last year. Geert Wilders, the Dutch anti-Muslim firebrand, is a guest author on the site.
Bolton was the chairman of the Institute from 2013 until his selection as National Security Adviser to Trump.
2) The BuzzFeed article below describes the connection between Gatestone and Breitbart London, RT (the Russian government-backed media outlet), Voice of Europe (a blog that disseminates anti-Muslim information in 18 different languages), and a number of smaller websites with names like the European Post and Gates of Vienna. From there, stories can travel quickly throughout the wider conservative media ecosystem.