I understand that a Cromwell navy is in much better condition than a ''restored'' Charles navy and because of that the outcome of sea battles are much likely to end in the favour of the English.
But if you want to let the Dutch lose, let them lose battles in a more realistic way. And avoid thing as sacking of Amsterdam. Amsterdam was already in the 2nd half of the 17th century hard to reach by the Zuiderzee for mearchant ships, let alone a complete war fleet of much heavier English war ships.
If you want to sack an important Dutch city, take The Hague, a large village, gouverment seat of the Dutch Republic, the only city not fortyfied and easy to reach from the beach by a landing party.
Admiral Wassenaar OBdam was the one of the few admirals with not so good qualities among a large number of very good Dutch admirals of that time. Cornelis de Wit never was an Admiral, Witte de Wit was, among many others, since a Dutch battle fleet was a combined war fleets of a confedration of states.
Most likely way of beiing killed at a sea battle was losing limp by a cannon ball, only the lucky ones were shot by a musket.
How about the fire of London, thos this stil occure?
And since wars only can happen if you have enough silver, how is the economic and financial situation of England.
I am sure it would not by so bad as under Charles IOTL, but the Dutch Republic is on its zenit of power, financial a behemoth with an, for that time unprecedented financial credibility, which was the reason why a smallstate as the Dutch Republic could wage somany wars, build war fleets from scratch at record speed andmuster large armies.
The methods of building ships in the republic was close to industrial methods, and was many times faster than other nations.
English war ships were much larger than Dutch ships. Both had there advantages and disadvantages. Dutch ships were build with excelent sailin quaility and suitable for shallow waters like the Dutch coast. The English ships were less manouverable but carried more guns ( thats was one of the reason for line of battle) and had a deeper draft. This made it risky for the English to aproach the sand banks ridden coastline of the Republic
How about politics, this King Cromwell must get envy of the French King and if the Dutch are loosing this war they could set up coalitions with France, Spain, Sweden etc.
Again I understand the quality of this English fleet, but the English are fighting for a political goal of a King, like Charles IOTL, the Dutch are fighting for their existence and life and bread.
The Dutch were convinced of the idea that the sea is from all. They only want free shipping lanes and good trade agrements and trading post, they were not interested in glory or empire.
Even the purse of the Dutch is much deeper than the English they will ask for peace, (war is bad for profits) and will agree with this, as long as this not hamper their trade or free movement on the seas.
One last thing, King Cromwell doesn't mind to fight an other Calvinist nation, while there are so many Catholic nations?