The deck load is 40 psf Live Load + 10 psf Dead Load. Deck loading is shared by both the beam and the ledger board. You would need to determine the area of the deck that is supported by the beam. This is affected by the location of the beam in relation to the end of the deck and in relation to the ledger board. For example, if the beam is located 1 ft. inboard of the deck end, then the beam carries more load than the ledger board carries.
The city chart you mentioned can be useful, but only if your deck is configured exactly like their assumptions. Otherwise, the chart is either conservative or non-conservative.
If you have concerns on whether the existing condition meets Code, I suggest getting an engineer to do a proper beam calculation using exact dimensions and spans, and correct beam allowables for live and dead loads. Or, just add a mid-span post to the existing beam to shorten the beam span.
The city chart you mentioned can be useful, but only if your deck is configured exactly like their assumptions. Otherwise, the chart is either conservative or non-conservative.
If you have concerns on whether the existing condition meets Code, I suggest getting an engineer to do a proper beam calculation using exact dimensions and spans, and correct beam allowables for live and dead loads. Or, just add a mid-span post to the existing beam to shorten the beam span.