Some general advices on your list:
- 'eavy armor for sloggas is generally not worth it
- You absolutely need a Painboss
- Equip a relic.
DLS is amazing if you get into mellee. Has proven to be the one of the best artifacts ever. Another one worth mentioning is Da Finking Kap.
- Make at least one centerpiece squad or 30 boyz with
pk Nob + Warboss + Painboss + probably a slotless mek. I prefer this squad to be choppas without special weapons as they tend to run and get engaged in mellee more often than not.
- Other squads can work in smaller numbers. I prefer ~20 strong shootas +
bp Nob - often with
pk -
pk is advisable but not mandatory for all the squads. Special weapons can be used effectively in here. I prefer rokkit launchas for utility.
- I'd advocate against burna bomber. You'll end up with lobbas or
kmk sooner or later anywayz

If you allready have a plane, i'd make it Blitza Bomber. s7 ap2 armorbane large blast that is a Bomb is decent. Since it's a bomb, it can be dropped while jinking and target invisible units. More useful than s5 ap4 bombz in general. And is cheaper cause you don't need to purchase missiles to be effective
- Drop
RPJ. It's useless. If you want to field a wagon - don't overinvest in it. Generally you're looking for just a ram. Can add boarding plank and one rokkit/shoota if you feel fancy. Other upgrades are a waste, unfortunately. You could probably utilise Killkannon but it distracts you from the main purpose of the wagon - troop delivery. Can be still used to great effect within blitz brigade but you ain't going for it with snakebites, i guess.
- Consider mek gunz. They're very effective and fluffy - especially for a snakebite-themed army. They're famous for their grot herding and artillery corps. Even though, original artillery pieces cost enormous ammount of money, take note that they're basically just orkified guns.
Historical models + Orkify = 5-10 times less money spent than buying original guns. You still need artillery grots though, but you'll figure something out.
And what's even better, artillery + footslogging boyz work!