Aye xbally,
This is becoming a saga! :'(
No petrol resistant lacquer on a tank paint job, leaking petrol cap seal and now a naff weld, with "monkey metal" to seal the pin holes. Someones gonads need a pair of Mole grips applied!
I suspect reparations are not easily come by?
So, in IMHO, remove tank, petrol taps and other fittings, purge, get the neck welded up by a reputable welder and a new two pack paint job, finished off with at least two coats of fuel resistant lacquer. The alternative is a streaky tank, with the potential to ignite!
Sorry to be the pooper to the party.
Good health, Bill