Very good guide! Two tips:

1. On Turn 1, move the archer unit out of Asaak, and ATTACK the Pahlavan army with it! Why? Because attacking Pahlava will allow you to keep Baktria, Hayasdan, and Pontus as your allies! Now, fight the battle yourself. Put the archers on top of a hill, but near the treeline. Switch off skirmish mode. Now, fire on the horse archer units as soon as they come into range, and ignore the Pahlava FM when he charges, just keep shooting. You should kill nearly as many men as you lose yourself, despite being massively outnumbered and outclassed.

2. I'd still be inclined to give Marakanda and Alexandreia-Eschate to Baktria on Turn 2, destroying all buildings first and moving your troops out. Why? Two reasons.

A, it gives Baktria a border with Pahlava. If Pahlava attacks Marakanda, they'll end up at war with Baktria, which would be great from your point of view, you could use the help! Also, it removes your border with the Saka, enabling you to make peace with the Saka. You don't want to fight the Saka until after Pahlava has been destroyed.

B, giving these territories to Baktria forces Baktria into a savage war with the Saka. The big Baktrian full stack army, instead of going after Kophen and from there into India, will likely be recalled to go to Sogdiana to fight the Saka instead! This stops Baktria expanding into India and making themselves rich, and keeps them busy fighting the Saka on your behalf, which is what you want them to do.

The idea is to sucker Baktria into fighting against the Saka and Pahlava instead of going to India. To accomplish this, it's worth giving them two poor provinces. It's a strategic trade-off. They are your ally, and nominally still your subjects, so it's still good roleplaying to give them territory to defend.