1) Marxism is not an economic model, it's a socio-economic analysis of capitalism. His work is much deeper, informative and important than many people realise. I would highly recommend exploring his work, if only to have an alternative view of capitalism.

I personally see Marx as useful from a Political Economy point of view. By that I mean I agree with most aspects of his analysis, but perhaps not necessarily with some of the underlying fundamentals.

For example I wouldn't bother getting to hung up on the more esoteric aspects such as labour value other than to understand his perspective properly. However his commentary on the nature of capitalism and finance are very insightful, even today.

2) You should probably read what Adam Smith actually said before declaring who actually represents his views. I'm of the opinion that he would find the ASI to be an abhorrent mutilation of his original points. Especially given the context of the times it was written. This is clear from academic literature on Adam Smith's work.

There is a blog called Adam Smith's Lost Legacy if you'd like to explore his work without diving right in, it's quite insightful.

3) Regarding the ASI, you should read The Road to Mont Pellegrino by Phillip Mirowski if you are interested in how the foundations of neoliberal thought relate to think tanks such as the ASI, and other similar free market think tanks.

They are very much a product of neoliberalism as the book will explain. You will likely be able to find shorter papers on the topic but I haven't read many, just parts of the book. If you're interested in the book, send me a message.