Thanks for your support, and glad you're enjoying the game and tutorials! You might try updating to the latest prerelease here (ZF), the bombers are a bit more sturdy in that version and will be easier to send against the Forts. Although, if you are playing 2.0, Raid Starships are more powerful against forts, so you could also go that way.
One thing I would suggest is playing on maps that are at least 30-40 planets. It's not like you have to take all of the planets or anything, but those and up are where you really the most out of the game grand-strategy-wise in particular. Roadblocks like the one you've run into are easier to work around, etc, too. In general, I feel like the really small maps, 10-20 planets, are sort of a different (but still fun) game that in some ways is harder (harder to get lots of ships at once, harder to unlock as many techs, harder to get around high level planets) and in others easier (easier scouting and grand strategy, reaching the AI home planets in general).
Hope that helps! I'm sure others here will have other tips, too. But if you're just starting out a new game, I'd suggest a 40 planet map as the "sweet spot" for a shorter game. Personally I always play 80, but those are more middle-length games rather than shorter. Happy holidays!