Alas; this question might be better suited to /r/HistoricalWhatIf; it has been removed here for falling afoul of a rules against speculation.

Stephen Bungay examines this question in detail in his book "Most Dangerous Enemy" (recommended if you'd like to read more).

Many believe that Hitler's order to stop bombing airfields and switch focus to London was the main reason that the RAF won. Bungay doesn't agree. I can't really sum up the entire book but in short the sticking factors are:

Airfields are difficult to destroy - you can bomb them but the holes are easy to fill, leaving a serviceable strip.

The "chain home" radar network and (more importantly) the command/communication network behind it was very difficult to destroy - Biggin Hill was the only sector station taken off air and even then for a few hours.

Between July & November 1940 fighter command actually increased in strength by over 40% in terms of pilot numbers, yet between August and December German fighter strength dropped by 30%.

Certainly the switch to attacking London took the pressure off the RAF but I don't think they were at breaking point.

I don't think either side was set to win from the start but maybe it wasn't as close run as some sources would have you believe. I also don't think holding off of Barbarossa would have helped - maybe that would have helped an invasion if Sealion had gone ahead but not in the air war.