Sounds like you're doing a lot of the right things already. Kids can be right little sh1ts so teaching them about respect and humility early on can go a long way. Building a rapport with the opposition coaches usually helps too as you'll probably find you're playing the same teams a few times each season, so if you can get on with them it'll help, especially if there's a bit of a mismatch in ability on the pitch.
For your match subs, we set up rotations to ensure that everybody gets the same amount of game time (or as close as possible to), although this only really works if you're dealing with kids that are all similar ability. If you're able to do that and explain it to them (showing our lot the spreadsheet I'd drawn up helped with this!), and they can see it happening over the course of a few games they should accept it.
For resources, the stuff you get with the FA level1 course is useful, although it tends to focus on individual drills and activities rather than teaching through matches. In our coaching group we tend to come up with a lot of stuff ourselves, and make sure we're picking up ideas from the age groups above us (and passing stuff onto those below us).
We had a mentor from the County FA with us for 6 months last season, which was great. He was saying their focus now is more on development through small-sided matches and thinking of ways to focus on particular aspects within a small-sided game, rather than isolated drills where you might just practise shooting or passing (which is what you get taught in the level 1!).
The general idea is to vary rules within a match setting, using something called the STEP principle, where you look to vary one or more of the Space, Task, Equipment or Players you're using to challenge them within the game.
So for example if you wanted to work on positional discipline split the pitch into three zones (defence/midfield/attack) and have players assigned to zones that they have to stay in (switching the players between different zones every 5mins). A good variation on this is to only enforce one team to stay in the zones and allow players on the other team to go where they like. They'll probably find the free roaming team all end up in the attacking zone and if the other team are able to get the ball they'll have players spread across the pitch they can press with. This can create overload situations in all areas of the pitch too, which is good for possession play.
For quick passing and play use either a 3-touch or 3 seconds with the ball rule and make the pitch smaller so there's less space.
If you wanted to focus on attacking support set the pitch into three zones again and have a rule where if a player dribbles the ball into the final third they cannot shoot, they have to pass first, which will get them thinking about passing the ball forward into the attacking zone instead and having the players without the ball making sure they come up the pitch to support the one with the ball.
For a possession game, set out uneven sides and make the team with more players have to complete 5-6 passes before they are allowed to shoot.
Doing it this way means you don't get the kids moaning because they're not playing a match too!
I can sit there all day and come up with stuff like the above, but the most important thing is to prepare what you're going to do *before* the session, so you're not having to think on your feet.
For more ideas we just tend to google for inspiration and then tweak depending on what we think our age group can cope with. There's a good resource here for example that you can get a lot of inspiration from: http://www.thefa.com/-/media/cfa/huntsfa/files/coaching/documents/fa-level-1-and-level-2-arrival-activities-and-game-related-practices.ashx (PDF download)
With our coaching setup we tend to run three different activities, split the kids into three groups of 8-10 and rotate them between each activity for 20min at a time so they don't get bored. This also makes it easier from a coach's point of view as you only need to come up with one activity and repeat it 3 times.