B40 tank queries

[hoogerbooger]

1) I lined the tank with POR15 a while back, but unfortunately sealed it too low to coat the tank filler mouth......so that got an undercoat and spray with cellulose paint. Whilst the liner looks fine, the fuel/fumes seem to get into the paint, make it soft, so that it has cracked and peeled....and the cap seal sticks to the remaining paint.

I presume it would be best to remove that paint.......but what can I paint on (by brush....for ease) that will not be attacked by the fuel [I have/will be using ordinary unleaded with millers VSPe Power Plus additive]

2) Is the B40 tank just a bonkers-cheap skate design that leaves a third of the fuel cut off from the tap ?  or did some have a reserve tap fitted ?