Tip: while in your case you still have to type something to get rid of the selection, you don't have to put !g at the beginning, anywhere in the query will do. I mostly put it at the end.
Instead of clicking you can use / or h to focus on the search field, press [right] arrow key and your preferred bang (!g) to open in google, no need to add any space to the last word (as you said).
If my search bar DDG search doesn’t return satisfactory results, I hit my address/search bar key (cmd+l for me), press left arrow/start-of-line key, type “!g “ and hit return. That gives me a google result page quicker than the time it would take to reach the mouse. It’s become a good workflow.
I’m having to use it less and less. DuckDuckGo is getting really good.