Sadly, I cannot give an answer to number three, as i'm from Excalibur

That said, there are a few ways to get seals. There is Caravan Defense, the most popular method, get a few friends and go to the low-level caravan camp, it should give about 300~ I think.
There are Company Leves, I think you're all of one level too short for the low-level ones as they are level 30 and believe me, archer trying to take on a leve four levels above is pretty painful. That said, company leves should be giving like 40~50 base, with more per difficulty level. As high as 240 at the L40 camp at max difficulty.

When to worry about DoH and DoL? Whenever you wish, really! That said, it might be useful to level your carpenter simply to make arrows for yourself but not at all 100% required, i'd say after you're done levelling your fighting class is a good time! It's what I did to mine.