How's it going?
Same age gap also between mine (youngest now 18m) and I remember it felt like a nightmare! Pulled in both directions and sometimes with us all crying :(
It took what felt like ages for ds1 to adjust to being on his own while I settled the new baby. DP was away for 5 weeks too so it felt crazily hard.
But it did happen and they both got the hang of it eventually, pretty much like RillaBlythe, except I used a favourite dvd for ds1, which seemed to keep his attention for longer. Reading all together just never seemed to work for us, but ds1 & I had reading time together when ds2 was asleep, though it did get interrupted at times!
My best tip is to make sure the eldest knows when their prime one on one time with mum is, and to try and make it regular every day. It is hard, but it can really help them transition.
DS1 is now at school and they both go down together, ds2 without boob, which I never in a month of sundays thought would ever happen!
Really good luck! Oh, and record your favourite programmes that you're likely missing and have a glass of wine waiting!