Hi Bargus - I know you posted this series of questions some time ago; so though by far not an expert player of this game, I do have a few thoughts.
This is a game about attrition. The number one goal is to keep your army alive and functioning.
As in all AGEOD games the Objectives should guide you. Select an Objective City and center this year's campaign in taking that city.
Because this is a game of coalitions, isolating a faction and defeating it, if possible, is a good idea.
You have laid out some good thoughts about plans. So I would put your #1 and #2 under how well they would support taking your key Objective City.
#3 - Yes, but you are not weak. If your plan is to wait for England and the Netherlands, where do you want your army when they arrive; close to cooperate or distant to force your opponent to separate or lose critical territory.
#4 - I rarely build anything except replacements, except for supply wagons.
That said, this game challenges me more than any other AGEOD game. One way I began to gain some progress was to pick a singular objective city each campaigning season.