is the best resource on EU Parliamentary votes. There's a Commons Library note on how to get the best from it which I can't lay my hands on at the moment. I'll post a link if I find it.
The data you require - the proportion of EU law that was opposed by British MEPs - isn't available, or at least not that I can find. I suspect that, if anyone had run that kind of analysis, one side or the other would have used it in the referendum debate, or if not it would have turned up in a Commons Library briefing paper. It would be a highly labour-intensive task to go through every EU regulation and directive, find the relevant vote in the European Parliament, and compare the votes of the British delegation with the result. It would be possible but not very informative.
Remember also that the majority of British MEPs aren't from the same party as the British government: so an EU law may be supported by the government, but opposed by our MEPs.
The EU makes two kinds of law: Regulations
which have direct effect, and Directives
which are, in effect, instructions to member states to make a particular law themselves. Britain has to pass an Act of Parliament, or introduce secondary legislation, to bring a Directive into effect. When we leave the EU regulations would cease to have effect, which would leave us with no law on those matters, so the government proposes to pass an Act of Parliament (the "Great Repeal Act") to preserve all EU law as it is when we leave.