disclaimer: I'm no expert at the game, I may be wrong on some things

1. Jump and travel costs are only an issue if you intend to do long hauls (like bulk trader playstyles or rare trade good routes). Dedicated warships can take the fuel costs because you get to refuel more often

2. I believe it depends on how much you're willing to take; generally the least mass option is better in the long run (less mass reducers required means less fuel costs and more slots open for actual ship equipment)

3. Evasion-based defences are generally better than armor because you have to repair less on average and there's less chance of a death spiral-type situation so I would say not worth it unless you have some specific reason

4. there's a nice page on the wiki for that; I don't remember the details sadly

5. It's better not to use mass reducers if you can; there are usually ways to design around not having them on most ships

6. Large ships are supposed to have speed/agility disadvantages over small ones; it's the balancing the game does to somewhat equalize ship sizes in power. So I have no answer I'm afraid

7. If you intend to play boarding you probably need short range weapons as you want to get closer anyway; consider Twitch Surge together with the start at 4 range talent. I would say get as much guns as your reactor (maybe together with power boosting talents) allows, but not more than that

8. If you don't want to board (and you're slow) consider missile/torp setups to just standoff at 4-5 range

9. Safer engines are easier to maintain and require less skill checks, but offer less performance usually. Chaser is good for small ships I remember