Wow, pretty ballsy first cook !!!
Looks amazing, your ambitions were rewarded !!!
Agreeing with an earlier poster, for some of the longer cooks I just pull the whole middle section and add coals, either lit or unlit depending on the situation. With insulated gloves its pretty easy, probably easier than removing the racks of meat.
As for the upgrade question, depends on quantity, I have had an 18.5 for years and haven't needed to upgrade, and I frequently do multiple cooks for a party. I find gaving multiples (kettle, spare smoker, gasser) etc is more beneficial than one big boy.