It's just a mistake that the canal symbol is missing. If you look at the second edition rule book, you see the canal symbol on a level 1 shipyard:
The rules also say
If you have just completed the Canal Period then remove all canal
and Tech level 1 Industry counters, along with any cubes on them,
from the map.
No mention of the canal/rail road ...
The extra amount is in additional income, in squares. According to the publisher's website:
if you sell to the Distant Market then the additional income shown on the Cotton Demand track is added to your income level, it is not taken as cash.
And further on, clarifying that you go up by squares, not bands:
When you gain income you go up a number spaces ...
I posted 25+ bullets on Brass strategy here. The Cliff's Notes:
Build only 1-2 level-1 industries. Develop early and often. Do not build the L1 Shipyard or L1 Port, period.
Build as few canal links as possible
Location cards are more important than Industry cards in the Canal Phase; the opposite is true in the Rail Phase
If stuck at end of Canal Phase, ...