My guess: Block heater is missing so there's a (temporary) hole in your engine. As for the engine not running well, complete wild guess, but perhaps the block heater melted a big hole in your intake after the butterfly valve. With no vacuum the engine will run poorly and not idle properly at all, but will run (sort of) at near wide open throttle, since at that the engine will be receiving enough gas to turn over properly.
With no vacuum, the brake booster will not function, which means you lose power brakes. Braking with no booster does feel a lot like no brakes at all. I bet if you push with all your might the brakes will work... poorly.
That's my guess. You will definitely be looking at flushing the cooling system if any of that mess ended up in there, you'll want to refill it, and you will want to inspect the intake manifold for damage and possibly replace it. But that's a total guess. Don't do any of that work until you've had a good look.
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View my fuel log 2015 Mirage ES 1.2 manual: 41.6 mpg (US) ... 17.7 km/L ... 5.6 L/100 km ... 50.0 mpg (Imp)