You have several questions:
1. Right bike from RE for a tall guy like you..
2. RE for 60+
3. Long silencer with short silencer, which is best one ?
4. Oil leakage issues in new RE ?
For answers:
1. It is completely based upon your choice, as per personal experience and view, new thunderbird is most comfortable among all RE and is better for long rides. But I suggest you to go to nearby RE showroom and take test ride of all.
2. In our group, we have some 60+ members, one has recently purchased Royal Enfield Std. 500, he is happy with it but has been riding RE from many years already. Another 60+ member has purchased RE thunderbird and he is happy with it.
3. It is again your choice, generally people go for after market product, glasswool silencer is preferred if you don't want to make noise but still want thump. Dealer can change silence for you , but will charge for it , moreover chances are they will use same after market silencer which you can get yourself.
4. Well, there could be slight leakage, even in new one but generally get solved with few services, will not be much issue though.
