With Sweden i believe it's near impossible to avoid war with one of the said factions.. I've done a few different things to win them over..1 sccenario: offer military alliance with Denmark and offer the Estonia region (they insta accept) Russia you trade St Petersburg for Karelia and Don Volsko. (then you have another fur trading region aswell) this scenario allow you to remain allies with Russia and Denmark for as long as you want and since you do not share a border with Poland they will usually stick to themselves and their war with Austria/other factions.

Scenario 2: Very first thing you do is place your troops near Stockholm and the ones in the city in your fleet.. Then click on Copenhagen the Danish capital and your fleet will sail to Malmoe (your trading port) autoresolve the battle and voila you got yourself Denmark in turn 1. Then put your fleet on the arrow so the Danish troops on the Danish mainland can't reach you. A thing to note though is that Russia will follow Denmark to war no matter what but at least you already got the Danish capital now and are in a much stronger position.