For Q1, you can’t delete Fixlets that are in External Site (the ones we publish). You can Hide them, remove them from Baselines, or choose not to Action them.
If you’ve previously deployed the older Chrome version, that download should be cached on your Root Server and the Fixlet would continue to work, using the previously-downloaded file.
That leads into Q2. Ensure your Root Server is configured with a large enough download cache to handle your expected patching load (whether your cycle is weekly, monthly, etc), and take an action from the Chrome Fixlet soon after its release (targeting any computer, even just one) so the file gets cached and the Fixlet can then be used indefinitely. Patch Policy is a good way to get the download cached.
If you always want to download the latest version of Chrome, I posted a task to BigFix.me for that. It downloads whichever version is current as of the time you take the action - but because I don’t know what version that is, there’s no version detection relevance on the Fixlet and we can’t validated the downloaded installer’s hash value.