Well, let's regard an imaginary scenario that Satalin might consider. Suppose he rejects proposal to sign the not aggression pact with Germany or/and the secret protocol to it.
What Berlin and Warsaw could do?
They could conclude secret agreement. Taking into account their cooperation to divide Czechia, it looks from Stalin's point of view as not absolutely impossible.
1. Pre WW1 Polish German border is restored of course including Danzig.
2. As a compensation Poland receives 2 fold larger lands in Ukraine and Belorussia that were for centuries parts of Poland.
3. Germany and Poland stage joint aggression against the Soviet union.
4. Germany gets Crimea, lands near to it, including Donbass, Kuban, Caucasus, Russian lands.
Germany used Romania as an ally. So why it could not use Poland in the same way?
Taking into account power of German armed forces and 1 million strong Polish army, such a joint aggression that could and likely would be supported by Western powers, would be a mortal threat to the Soviet union. Of course, Stalin preferred to stimulate a war between capitalist countries and prepare to future inevitable war.
All your putative (Putinative?) points have already been covered and consistently debunked in this thread. They are a prime example of one of the principles of the Muscovite Mindset. namely: "Everyone is out to destroy us, therefore we have to destroy them first".
Moscow appproached Berlin with an offer for what became the Molotov-Ribbentrop Pact, not the other way around. Stalin did not consider the proposal, he initiated it.
No secret agreement between Poland and Germany was possible as there were mutually non-negotiable overlaps. Therefore no joint aggression. At no stage in the run-up to WW2 did Poland repudiate its non-aggression treaty with the USSR or even accede to Berlin's wishes and join in various defensive agreements with Germany alongside other central and eastern european states.
Berlin wanted Belarus and Ukraine for itself
Poland did not cooperate with Germany to divide the Czech Lands. There was no joint operation. The Polish Government took advantage of the German operation and annexed a small sliver of territory it had claimed since the end of WW1. Not a noble action by any means, but not the active collusion with Germany as depicted in Moscow.
The Western Powers would never have supported a further aggrandizement of German Power eastwards. The Munich debacle had been the final straw. Hence the French and British security guarantees to Poland.
However, you are quite accurate in your last sentence which absolutely confirms that Stalin through his proposal of of the Molotov-Ribbentrop Pact and its secret protocols (essentially amounting to a of a de facto alliance with Nazi Germany) which Hitler avidly and quickly accepted; enabled Nazi Germany to invade Poland and thus initiate WW2 by the trigger of the previously mentioned French and British security guarantees to that country issued after Hiter had reneged on the Munich Agreement.
Stalin assessed that Germany would exhaust itself and its opponents in a war against France and Britain a la WW1 while maintaining its pact with Soviet Russia through the necessity of avoiding a two-front war. He would then be able to steamroller the Red Army to the Atlantic at the time of his choosing.
It didn't quite work out that way, but the Kremlin managed to claw back and partially achieve its war aims, partly due to the huge (and intentionally unacknowledged by Moscow) aid it received from the West post-Barbarossa and due to the naivety of the USA in taking Stalin's propaganda, lies and blandishments at face value.
Moscow was completely implicit in the outbreak of hostilities in WW2. It's dreams of conquest, territorial aggrandisement and world power mirrored Berlin's. Each of these despotic dictatorships believed it could use the other to achieve their aims. Poland was in the way. Therefore Poland had to be obliterated first.