Would Feral Orks be able to create/use:
I'd say that Feral Orks could use all of this stuff however you'd have to redesign the item names and descriptions. Instead of a syringe a feral ork would probably ingest some crazy 'shrooms and it would have the same effect. A wreckin' ball would probably be a massive log or boulder suspended from something.
If there's something to be done then an Ork will usually find a way to get some poor grot to do it; lugging around spare arrows, re-tightening the vines which are holding the chariots together etc. and all Ork civilisations have grots running around.
'Tankhammers' is the only one where it might be a bit harder to come up with a feral alternative but given that they can only be wielded by tankbustas with rokkit launchas you probably wouldn't be using them and if you were you'd have come up with a feral version of the rokkit launcha, whatever that is just attach it to a stick and you've made a tankhammer.
As for the stikkbombs, I've never seen them used, the only things slower than you are power fists/axes etc. and if you have a tide of greenskins (which you should) then a lone sergeant with a fist won't make too much of a dent. For this reason it's also quite a good idea to have bosspoles, if you fail a leadership test then you have to flee, maybe even break from combat and you don't want to do that with orky initiative. You have a green tide so you might as well throw away one ork to keep the rest of them stuck in.
Ammo runts, yeah they probably aren't in most cases however if you were to get a Big Mek with a Kustom Mega Blasta (which gets hot) or your Warboss really wanted to take out a transport with the lone rokkit on his kombi-weapon then maybe it would be worth it. I think people usually take them when they have a few extra points left to spend at the end of constructing their army, given the feral nature of your list you can probably forget about them.
I'm not sure about things which I wouldn't expect to see in a Space Ork army, maybe Big Gunz, lobbas in particular (catapults).
Hope I've been of help.