Hello and welcome! Mmmh, I am with an agency in the mo because I am only a very part time hussie. Whether it is better to work for an agency really depends on who actually runs it and their attitude towards you, i.e. your safety and whether they are going to put your welfare first or if they will always side with clients. My agency lady is lovely and very understanding since she done escorting herself. Personally, I believe that is a bonus as this at least in an ideal world would make her more sympathetic to your needs. However, I am contemplating also setting up a basic template website to freelance too or instead. Simply as the agency is not really around on the weekend and times I am more likely to want to work. The agency owner is also not that Internet savvy (bless her) and thus tends to not update her website in regular enough intervals. I now have had an incall place to work from all the time for 3 months yet my profile still only refers to Mondays which does not really help to promote me as effectively. Perhaps you could try both avenues.
As for size - I think 12 is lovely and is likely to appeal to a wide cross section of men. As for the Fetish scene - mmmh, I would really make sure you actually research well what this type of work entails and if you are really comfortable with it. Leather and PVC in itself are just more of a fashion statement that is becoming quite main stream. As for any service being part and parcel - remember you decide what you offer and are happy to do! Don't let yourself be dictated by what may be perceived as the general trend.