Hello Sandy,
what is your goal? To connect only via Eclipse to HCP or do you wanna also use the console client and/or develop Java Applications? In the first case, just the cloud tools from the repository are necessary I posted in my first answer (you have to install them via the "Add Software" mechanism in Eclipse).
In case you wanna use e.g. the Console Client or develop Java Applications you need the Java SDKs (as you mentioned e.g. Java Web). But that is the second step after the intalling the cloud tools.
The SAP HANA Cloud Connector is only necessary in case you wanna connect something from your OnPremise Landscape (e.g. an OData service from an ABAP backend). It is not necessary for the connection of Eclipse to the HCP.
Regarding the SAP JVM you can download the version you wanna use. By default I would use the newest version, but because of some pre-conditions regarding your system or applications you wanna develop a lower version could be necessary.
At the moment instead of Mars I would still use Luna, cause not all tools (like the HANA Tools) are released yet for mars. So if you wanna e.g. also use HANA specific features of the HANA instance in the HCP, it is not officially supported for Mars. Check the overview on page SAP Development Tools for Eclipse for the current status and updates.
Best Regards,
Florian