Correct, rewards come from the creation of a block but even if you have no delegators, your 1m+ pledge will still count towards the stake in your pool and the corresponding probability to be allocated a block based on that amount.
Current epoch the average stake required to make one block is ~2 - 2.5m stake (d=0.68), slots are allocated based on a lottery which depends on the amount of stake you have so there is no guarantee.
So with 1m+ in stake from your pledge on average you might get a block every 2 or 3 epoch but you might also get more or less lucky.
For each epoch you make a block you will get rewards, for epochs where you don’t make a block there will be no rewards.
Yes, but imagine this example. You have only 1m pledge and nothing else and assume you will create a block only in every 3rd epoch (due to that 1m pledge) that means you wont get rewards in two epochs but much higher in the 3rd (around triple of the expected), which would average out for that ~6% ROI per year. Hope it makes sense.
Of course assuming your pool creates its blocks when it is scheduled, i.e. online 24/7 and not loosing any blocks for different reasons (slot or height battle etc.)