You MIGHT be able to ripen any crop if you spray them with Bordeaux mixture, but you will need to wash off any copper deposit on the skins of the tomatoes.
The only real 'cure' is a period of hot, dry weather which is what has happened here where we are in France. Like you I'd cut off all the affected blight on the outdoor plants and the new growth is now flourishing. But the chances are the plants will succumb if it's still humid and damp.
You don't need to sterilise soil as the blight fungus does NOT survive in the soil and is mainly spread in the wind from active infected material. That's why it suddenly spreads through a district once some gardens or fields are affected. I always put infected plants in the compost heap and have never got blight in that way; it's only in the wet, damp and humid years.
The one thing I DO believe carries blight from year to year is allowing the 'sports' of potato tubers to come up as blighted plants from the previous year seem to be able to carry over the infection. So never leave potatoes to come up from previous years.

Thank you that gives me some hope! very hot and dry at moment so we shall see.