The help article suggests that you can use our built-in jQuery with a jQuery plugin without the need to include another jQuery. Yes, you will use our jQuery, however, the configuration is straightforward and I thought you may find it useful. If you want to stick with your version of jQuery, then the workaround you have found would suffice.
As for the two RadScriptManagers, you only need one. The help article shows both ways - when you have a RadControl on the page (the second RSM) and when you do not have (the first RSM; you need to also add the jQueryInclude.js after the first two script references).
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