1. Currently there's no option to monitor memory usage at view level in Diagnostic & Monitoring tool.
Denodo Monitor Report has some info at view level granularity ([by_view](https://community.denodo.com/docs/html/document/denodoconnects/8.0/en/Denodo%20Monitor%20Reports%20-%20User%20Manual#h.n7xe9cqv3ybe)) but they includes only numrows, cache status, execution time, etc.. and no memory information.
2. & 3. Yes, excluding unnecessary columns bring lower memory usage, however it's much more important considering the difference between Streaming and Non-Streaming operators. Non-Streaming ones have the heaviest memory footprint, therefore if you're having memory issue you focus on them. The list of Non-Streaming operation is listed [here](https://community.denodo.com/docs/html/browse/8.0/vdp/administration/memory_management/streaming_vs_non-streaming_operators/streaming_vs_non-streaming_operators). Also, [this](https://community.denodo.com/docs/html/browse/8.0/en/vdp/administration/memory_management/edge_cases_in_streaming_operation/edge_cases_in_streaming_operation#edge-cases-in-streaming-operation) section of the VDP administration guide could be useful as it explains some situtation when increasing/decreasing the amount of memory of a Query.
Hope this helps