Okay, I just want to endorse your plan. It is absolutely NOT necessary to port every single level of the arcade version. I might argue that you have already ported more than enough!
The fact is that much as I loved the original arcade version, it does get VERY repetitive after the first couple of levels - and let's be honest, it gets quite boring.
They even start to recycle some of the first levels and enemies, just with a different colour palette etc. I suspect the original developers were asked to stretch the game out purely to keep players putting coins in the machine.
So, for the conversion, I'd say it NEEDS to be cut right down to keep the gameplay fresh.
And, as you've said, this is a hobby for you! You don't owe us anything - everything you've done so far is a bonus!
Yea that sounds about right.
Also, some of the enemy AI is pretty sophisticated when you study it and the platforming challenges are really well thought out too. It's just not given proper time to breathe since the game tries so hard to hurry you along all the time so the kid next in line can spend all his quarters too : P