As for G variant, there is a 2018 SAR document that envisions 160 airframes, so that should be about the right number even today. Unless those 160 include airframes for Australia. Do they?

The 160 number is for the USN (not including RAAF). The requirement went from 114 up to 160 and the last time the Navy performed an AEA AOA the requirements ticked up to 180 (another 20). The Navy is currently awaiting a Joint AF/Navy AEA AOA completion to determine whether to proceed to that 180, stay put or pursue a different number. Navy took the 160th growler delivery last year.

On the F-18E/F fleet, with the current Multi Year Procurement contract (72 aircraft + 6 prior year congressional adds) the Navy’s SH fleet will grow to 619 aircraft (this accounts for losses etc) so if you want to get the current count you can subtract all future year (FY20-23) deliveries and average out annual deliveries to account for aircraft delivered in 2019 so far..

Since no new F/18E/F SAR is required (because of quantities being below the threshold that triggers a new SAR) your best bet to dig up current and planned inventories and future plans is to look at the 30 year aviation inventory and funding plan which is usually updated (combined AF and USN/MC) with every budget.