2+6) It's been mentioned already, but there seems to be a bit too much money after a couple of years into the campaign. Along with the bump in construction prices it may be a good idea to bump samurai costs and/or cut a bit of income at the mid to top end. While the time- and cap-constraints on samurais are great, after a few years, there is no monetary-constraint on building samurai.
This is probably because I haven't gotten all that far in the campaign and because I haven't fought too many simultaneous wars or overextended myself, but after the initial couple of years, I don't find myself recruiting any ashigaru, at all. Maybe more restrictive capping of samurai is in order, or linking more closely the number of samurai to the number of provinces you own? Again, this may be just the particulars of my campaign.