awesome you are revisiting homerun and also looking at factors like it's 1.84KB size!
That is really significant for an Atari game - the isometric Activision Tennis game is also pretty awesome at 2K you should take another look at that one too imo - always had a blast playing it.
Regarding the tiniest Atari 2600 games possible there is an annual tiny video game contest in 10 lines of BASIC that is now open to the Atari 2600 (Scotland, I think you may be surprised at how far we can push the VCS today!)
Here are my entries for this year and last year, you can try them in the Javatari browser:
One Player Tron, (10 lines of BASIC):http://javatari.org/?ROM=http://relatio ... Player.bin
0 if g=0 then g=1:for x=18 to 239:virtualworld(x)=0:next x else f=f+1:goto 2
1 for x=0 to 9:g=g+10:virtualworld(x)=g:next x: x=10:y=5:h=1: rem (dir right)
2 if f<4 then scrollvirtualworldtoggle=0:return else scrollvirtualworldtoggle=1
3 if joy0left=1 then e=1:h=0:i=0:j=0:AUDC0=8:AUDF0=BITIndex:SUSTAINFORFRAMES=15
4 if joy0right=1 then h=1:e=0:i=0:j=0:AUDC0=6:AUDF0=BITIndex:SUSTAINFORFRAMES=15
5 if joy0down=1 then i=12:e=0:h=0:j=0:AUDF0=11:AUDC0=BITIndex:SUSTAINFORFRAMES=15
6 if joy0up=1 then j=12:i=0:e=0:h=0:AUDC0=3:AUDF0=BITIndex*2:SUSTAINFORFRAMES=15
7 x=x-e:x=x+h:l=i/12:y=y+l:l=j/12:y=y-l:BYTErowoffset=BYTErowoffset+i:rem TRON!!
9 if vwpixel(x,y,on)>0 then COLUBK=100:SUSTAINFORFRAMES=100:goto 6 else return
WarpDrive (the game, but not the scrolling text, is 9 lines of BASIC):http://javatari.org/?ROM=http://relatio ... VE_AFP.rom
If you include the runtime these Atari games total about 2k like the classics above but only because BASIC wasn't built into the console.