Mike, the website that you posted has an incorrect spelling, it is Pachypodium lamerei, but that is insignificant.
A cousin of Thea's has 2 in her garden that are over 2 metres tall. As far as we can remember they are a little over 20 years old. I have also seen others, of varying sizes, around the island. P. lamerei is apparently far more commonly grown than P. rutenbergianum which can grow to a height of 8 metres, so I think I would stick my neck out and go with the former.
As for the spines, the specimens that I know have them in threes, 2 pointing downwards and a much smaller one pointing out, if this helps.