RB30 timing issue

Hi guys, hope everyone is well.
So been making a bit of progress on the patrol lately, done an EFI conversion and got it running the other night. Anyway I realised I had set my H/B at 30deg adv, but it still started and ran a little rough to be expected. so I went back and re-timed it to TDC so I could advance my timing a bit with the dizzy, anyway no go! so at this stage I'm starting to think my belt has maybe jumped a tooth or two, so I adjust it back to 30deg adv to see if will fire again and wont start at all now?? I cant say when the timing belt was last replaced, but does it sound like this may be the cause? want to get some opinions before I go and order a new belt as it seems like a fairly big job!. Thanks in advance.
Ben

Pull the top timing belt cover off. Set the engine to TDC compression stroke for #1 cylinder. The timing mark /dot should be vertical top of the Cam pulley.

Disconnect the vacuum advance at the distributor while setting your timing.

Awesome I'll do that, but I don't have the vacuum advance now as I converted it to efi. Also read somewhere that when the engine is cold it will idle close to 30 deg anyway until it warms to normal operating temp, then will drop back to 15 deg or wherever you set it?. I'm going to replace the timing belt anyway as it has over 300k kms on it and not sure when it was last changed, but at least I know how to set the cam when I put it back together.
Cheers for the reply