Well I'm glad to see you've figured out most of what you were doing wrong.
Well I'm doing better in the colony rush anyway, though I'm still falling behind in tech. If I'm not number one, I'm usually second or third, behind races like the Thalen and Krynn. It's somewhat understandable with those guys given their bonuses. I usually cringe when I see the Thalen in the game, their cheap factories means they're able to crank out colony ships left, right and centre. I'm not that worried about the tech really because I can always trade for some of them, and once my colonies start gearing up, I should catch up.
And yeah most of the time financing ships can ruin you but if done right and with strategic goals in mind you can put yourself further ahead then without it. A lot of times I use it late in the game when I'm probably going to win in the next 50 turns or so anyway. Once you become supreme ruler of the universe no one cares that you are 1000BC in debt.
I tried fininancing once at the start, the first option with the shortest pay back, and my empire ground to a halt. I had to turn my production slider down so far I wasn't able to build anything. Last time I try that one! From now on it's "pay as you go."
Planetary bonuses are given out in an attempt by the game engine to *balance* out the map. There have been several posts about the *whys* of the random generator from Frogboy. Normally if you start out with a 300% or 700% on your home world you can bet there are no other really good planets within your starting range or you are completely surrounded by AI empires. A difficult position to be in but by no means impossible.
That's a good thing to keep in mind. Also a good way of having them in the game. A +700% manufacturing tile can certainly be overpowering.
The highest is 1000BC. Still 2 of those and you are set.
And still, I never seem to have much luck with those. Like I said, my guy always seems to end up on the other side of the galaxy.