Answer A size 8 is a 33-25 bust with a 27-29 waist; size 10 being a 37-39 bust and 30-32 waist. Based on your bust size and weight I would go with the 8. As you stated, your concern is the arm and leg length. This particular item does not come in a long version. We do carry a few "tall" suits. In a 3/2 we do have an 8T in an Excel Infinity suit - at this time very limited quantites. The price is quite higher.
Answer Yes, some wetsuits come in longs, but are hard to find. I found that I had to go up two sizes from my normal clothes size to get a decent fit. I normally wear size 6 and got a size 10. I too have long legs and arms and wider shoulders. This suit really stretches which helps. The arms are a bit short, but good enough for canyoneering. I also tried a men's small in another suit and it fit nicely in the arms and legs because it was slightly longer. This particular suit does come in a men's version which might work for you. I almost sent it back to get the men's version, but didn't have time.