I think it's only been a little more than a month since you brewed? No rush to move it out of secondary, unless you need the fermenter space. That's a big brew you have there, and sitting on the secondary yeast cake could help it smooth out a little quicker. Mine sat for months, of course I had nothing else to compare it too.
If you are going to bottle next week, you could probably get away with not adding any more yeast. They are a little stressed sitting in that much alcohol, so adding either T-58 or the slurry from the old ale gives some extra reassurance. I would personally go with the slurry from the old ale as its already used to some alcohol, whereas the T-58 would have a pretty big shock getting into your high abv RIS.