The extra queen lets you deflect stalker/zealot pressure while letting you also send one across the map. This push MUCH more powerful if you have creep moving up with your locusts. I do not get OV speed because I do not use OVs for creep and I don't really need to scout because I'm dead if it's a super fast gateway all-in and he's dead if it's anything else. You get all the scouting you need when your locusts are knocking on his front door.
I usually send 3 drones down to my queen/OV staging area to make spores that ideally finish just as my swarm hosts arrive. Again, PUSH CREEP! Locusts gain a substantial speed bonus on creep. I don't think you need more than 3 because you have a queen and can get hydras, which will be much more useful in the long run.
I watched one of your replays. Our builds result in a similar number of swarm hosts popping out around the same time. You had 8 at 10 minutes while I had 9. However, I don't think either of us has the build down to a science yet so this can probably be optimized. Because of this timing, we are safe against any 2 base play that pushes out later than 9 minutes.
I would say a good refinement would be to Overseer scout @lair 100% to check for Stargate. If yes, drop hydra den faster and get 4-5 after you have a handful of swarm hosts because they will prevent voidrays from killing locusts for free.
It's also very important to know to transition. After a certain number of swarm hosts (lets say somewhere between 10 and 15) you want to either start getting hydra or corruptor/muta. Hydra will let you break a player trying to push you back with air while you need either corruptors or muta to deal with colossi. Colossi are the correct answer to this build. I have had a ridiculous win ratio with this build, losing only when my opponent goes for colossi immediately after seeing my swarm hosts.
I would say that when you are getting to this transition point you also need to decide whether to take your 3rd or just to mass units and go for the kill. I like to fall back on the adage, "When ahead, get more ahead," and just take the 3rd. If the Protoss manages to break out with Colossi then you can be in trouble on 2 bases.