1. I'm really not sure to be honest mate, if you want to get into proper research then you will need PG qualifications and I think it is what you do then that will dictate what field your career is likely to be in. Personally if you definitely want to go into research I'd go with a standard chemistry degree at UG (will be way more interesting anyway), and then if you want to be an engineer instead pick a masters/phd project that is in the engineering field.
2. Yes, same as before, to go into research you will need PG qualifications, whether you are an engineer or a chemist will only influence the type of projects you are likely to be accpeted on.
3. I can't predict the future, but chemical engineers are highly emplyable. A chem eng BSc will generally find it easier to get a job than a pure chem BSc.