Gentlemen:

Finally I removed all the screws from bases (2) and rings (8).
Thank you so much for all your advise.

At the end, the solution became "mixed": direct torch heat was necesary to soften the glue, lots of torque aplied (2 men job) and 3 of the 8 rings screws needs to be drilled.
No damage even in the rings, only need to replace all the screws because they suffer damage from the strong torque applied.

Thank you again.

Best,

Jose M. Fernandez