I like your ideas very much.
Where in OTL the early 17th century for Portugal was mostly (if not a decline) a series of missed opportunities thanks to the Spanish personal union, this new and vigorous ruler looks to be taking them in a more aggressive direction.
The downside for Portugal is that Brazil will probably be smaller, as Philip III's boot will be on the neck of whoever draws up the revised Torsedillas.
Well, OTL there were many ideas of how should be the Brazilian border, since no one was very secure of how Tordesillas should be interpretated. Surely, now there will be an agreement much more in favour of Spain. Here there the ideas used through the 16th and 17th of how Tordesillas Line should be (repair in the Portuguese trying to curve the line):