Short answer: no, you can't assume anything. Food packaging can be pretty much any type of plastic, some of which are totally unrecyclable by their chemical nature.
It's possible that there may be some other use end use for nonrecyclable plastic - being shredded and incorporated into other materials for instance. Supermarkets and other businesses are ...
A 30 minute drive would be approximately 15 miles, an average small car produces 200 grams of CO2 per mile, so you are emitting about 3 Kg of CO2.
The CO2 footprint of new plastic manufacture is about 6 Kg CO2 per 1 Kg of plastic.
For recycled plastic manufacture its about 3.5 Kg CO2 per Kg of
plastic. So the nett difference is 2.5 Kg CO2.
Supposing that ...