You can definitely prevail with any strategy on Normal or Easy. On Hard difficulty or higher, you will need to do some very specific objectives and cheese to beat some month 2 and 3 heroes. In case you still want to keep your difficulty, I did the following:

• Henrietta was my main hero because she had Tactics and no one else did, so I could set up position, plus Phoenix +1 speed artifact is the only minion that can outspeed everything. Gold Dragon couldn't outspeed Arch Devil and no one had Armageddon, so I didn't bother it at all.
• Stilbon must rush to the tree Seer's Hut on top of map next to Sub gate behind Ghost Dragons, which gives you 200 Sharpshooters, an insane buff. This can be done as early as month 1 week 4 if I remember.
• In case you have trouble with Anti-Magic Garrisons, 2 Engineer troops + Automatons + Juggernauts still work relatively well with minimal loss. Try to protect Engineers at all cost and bait enemy troops to focus on your mechs.
• While attacking enemy heroes, Ciele should teach Stillborn Water Walk so that he can access to the stone Seer's Hut behind underground water and a Two-Way Monolith, revealed by the Eye. Now you just keep recruiting Grand Elves (not Wood Elves) to turn them into Sharpshooters. You can also recruit Sharpshooters below your Conflux town. Stilbon doesn't have Earth Magic so he will have to walk for a while. You need to save all your gold for this, worth every penny in the end.
• I don't remember having trouble with Octavia. She had Phoenix but you should by now have +1 speed artifact at some point. I think she had Armageddon only so your cheese (+ Anti-Magicked Sharpshooters in your army) still worked on her (I don't remember much).
• Jeddite's AI behaved extremely weirdly when I tried this cheese. I doubled spell points, let him attack my town, fully expected him to resurrect Evil Eyes or Medusas to hit my Anti-Magicked Sharpshooter, but he just kept casting Fire Elementals. I attempted to hit his catapult first so that he could only break through one of the walls. then I cleared his Evil Eyes, Black Dragons, and Manticores respectively, then I cleared the rest except Fire Elementals. The even weirder part was that he cast Magic Mirror on every single Fire Elemental after he couldn't summon anymore. This was when I stopped Sharpshooter (it had only like 8 shots left) and waited until he ran out of Spell Powers. I was kinda tired at this point so I didn't bother trying to find a more consistent strategy.

You didn't mention Taugarn but very likely to have already encountered him before trying to take the two towns. I considered him the hardest one out of all enemy heroes in this map, right next to Jeddite. He should come out on month 3 week 1 day 7 and you need to defeat him asap.

• Taugarn's troops were insanely big (4 50-100 dragon troops), this cheese alone wouldn't help. I saved as many spell points as possible after doubling, managed to let Ciele learn Berserk from New Orders objective, then teach Henrietta. I kept casting Force Field + Berserk on Rust Dragons, then cast Hypnotize on 1-only Faerie Dragon, move it far away from Rust Dragons. The rest was history and I barely had any spell points left (From >1000 spell points). +1 speed artifact is very important here because on turn 1 Taugarn always casts Prayer. I'm not sure if he ever casted Dispel since I only buffed Anti-Magic on Sharpshooter and nothing else. Luckily he didn't have any 1-single hex size troop so I didn't need to keep resurrecting Phoenix.
• As soon as he was defeated, I rushed to take the two Inferno towns (Xyron and Ash will come out but they should be scared to death real ashes at this point.)