Bear in mind as the petrol sold in the UK is now 5% ethanol there is some offsetting to the extra (you quote 20%) carbon emissions of a petrol engine. Some countries are even using E10 as it's called with 10% ethanol.
Unleaded petrol can still contain very small amounts of lead (and unleaded petrol doesn't account for 100% of petrol used in the world).
Your understanding of my understanding is clearly wrong as I agree with you - due to the extra demand for petrol, UK refineries are geared up to extract more petrol than diesel from a litre of crude oil. Thus, as I say, it takes more crude oil to produce a litre of diesel.
A modern 44 tonne tanker holds upwards of 42000 litres maximum capacity not 35000. They are therefore restricted to weight, carrying around a maximum of 37000 litres of diesel against 41000 litres of petrol, although this varies with temperature and density of the fuel on a daily basis.
Just to address your points.
1. Diesel fuel in the UK and across Europe contains between 5-10% biofuel as well it's a European directive so their is some of setting of CO2 emissions with either fuel, petrols still produce an average 20% more CO2 than diesels. CO2 causes global warming, makes the oceans more acidic and is responsible for climate change.
2. Unleaded petrol shouldn't contain small amounts of lead as lead had to be added to petrol, the refining process should completely remove any heavy lead particles that are naturally present in the crude oil and in 2013 leaded fuel was banned world wide, lead replacement liquids have to now be added after sale of fuels. Granted that the world is a big place and their may still be some corners of the world that sell a bit of leaded fuel but this is a tiny minuscule fraction of petrol fuel used in the world.
3. Extra demand for petrol over diesel means in order to produce more petrol than diesel refineries take diesel fuel and refine it down further to make petrol through a process called cracking. Basically producing diesel from crude oil is easy but to get the yield of petrol demanded by society diesel has to be refined further to make up the shortfall. So no it doesn't take more crude oil to make a litre of diesel but it takes much more complex and expensive processed to supply the demand for petrol.
4. Aside from the fact your maths on how many litres can or can't be carried doesn't really add up, your argument about tanker use is pointless. tankers are made up of compartments a 44 ton tanker lorry will carry both diesel and petrol at the same time in separate compartments and delivering both fuels to petrol stations.
For safety reasons you cannot drive a tanker about with half full pots as the fuel will slosh about and constantly change the centre of gravity of the truck and make it liable to tipping over, as a result when a station orders fuel they are only allowed to order by the quantity of a full compartment. So say a tanker has 6 compartments, because of the rate of demand for petrol versus diesel the truck may be carrying 4 chambers of petrol and 2 of diesel, all chambers will have to be full and will be emptied at the point of delivery.
It's worth noting that 42,000 litres of diesel fuel will weigh about 35 tons allowing 9 tons for tractor and trailer unit assuming it's a UK 44 ton lorry.
And still non of this is relevant because you still agreed that neither diesel or petrol are any better than the other when it comes to pollution/emissions.
Yes maxi I know heating oil is kerosene however kerosene chemically very close to diesel. Kerosene is comprised of hydrocarbon chains of between 12 and 15 carbon atoms in length and diesel consist is chains of 16 carbon atoms. Emissions wise they're not dissimilar.