Wow big update (kinda):
Let me start off by saying... RANDOM MY ***! The random numbers are hardly anything but random. I can't quite pinpoint them yet but after some testing I started to notice some huge patterns in the game which blow random out of the water.
When I was fighting the police I noticed a really weird pattern for my attacks. I'd hit for 28 five times in a row (retrying with more B-button presses each try). Then if I kept retrying, I'd hit for 29 several times in a row. Then 33 several times in a row. Then miss several times in a row. Then 31 several times in a row. Then (after 10-15 of the 31's) I'd CRITICAL a few(!) times in a row. But this happened more than once. On the first Cop, my bashes were in the 31 string (at the end of this, around the 9th try I got a critical). Then on the 3rd cop, I kept retrying past the 28's and 33's until I started to get a long string of 31's again, and at the end of the 31's (about 15 this time) I got that critical hit again.
I also noticed that monsters seem to do this to a certain point. The Titanic Ant would bite me like, 9 times in a row, but after that the next 5~ times would be psi magnets (remember I'm talking about retrying it several times during the same turn, not literally 'the next turn the next turn the next turn').
I still don't know how the variables work into this structure, but it's very confusing. At the same time it's satisfying to see an emerging pattern and now I feel closer than ever to nailing this sucker. I know that this is technically a Pseudo-RNG so it can't be true random, but this goes beyond that with the whole pattern-system. I just don't know how they're linked...
On the subject of 100% dodge-movie, after testing I discovered some Pro's and some Con's. The biggest con is that some monsters don't have a 'waste turn attack', which means the only way to get through those battles is either take damage or force them to miss. The miss isn't SO bad, but certain monsters will be using PSI on you (damage psi doesn't miss). Also, certain monsters have absolute-guarenteed scripts that screw this up. Example: when you fight Frank's Machine (Markenstein or whatever), it will ALWAYS do a pattern of 'steam, attack, steam, attack, steam, attack, steam, attack, steam, attack'. The only way around this is to force a 'miss' on it's attack turn. There's no way around this problem unless you can kill them in 1~ hit which can't happen (even with a critical smash) unless you power-level. I suspect other monsters later in the game have similar unaviodable scripts, but I'm not sure. Sometimes a monster will act like it's ONLY going to do a certain attack, but in reality it's just part of a long pattern-string that can be bypassed with enough b-button presses.
Well that's the CONs, what about the Pros? The biggest pro is that you can (from what I've been able to do) have a 100% monster-free map. The monsters that appear on screen can be manipulated quite easily just by going back-and-forth until they don't appear anymore. I was able to walk through the entire first dungeon up to the ant without having a single battle. And the bosses & forced fights give enough exp that there's pretty much never a need to power level or get into random battles. That's great! Also, because you can USUALLY force a battle to be 'perfect' (no damage), you can pretty much skip all healing food (loading up on psi-recovery instead), skip all armor (since you won't get hit, but status-protecting armor could be great to negate certain attacks), and fight monsters much much lower than you should really be able to. I was able to take out the Titanic Ant at level 4 (and I was only that level cause I had been screwing around earlier with testing). This also means that money won't be much of a problem since you're just buying weapons and skipping expensive armor.
On a closing note, maybe there's more hope for a TAS afterall. I said above that certain monsters don't have a 'waste turn attack'. The 4 Police in the station only have Attack and Chop (that's it). But I found that I was able to SMASH them for a 1-hit KO (if they got their turn first, I forced them to miss or dodge). So as the game goes on, with more party members and stronger attacks, maybe this won't be a problem. Time issues aside (pretty long game), I think a TAS run is totally possible with the right manipulation.
*Extra Update*
After viewing starmen.net (big database of earthbound) I found that each monster has a 'pool' to choose from when attacking. The reason sometimes that monsters seem to do nothing way more than they attack (clumsy robot, or belch after eating fly honey) is because they have duplicates in their attack list making it more likely for them to pick that. By checking each monster you fight, TAS becomes easier to know what to expect and what to aim for.
Also, according to the site, every monster has a 25-100% chance of being hit with a status effect. EVERY monster, including pokey, gigas, the sanctuary bosses, etc. Landing a 25% paralysis or flash on a boss could make a huge effect in the outcome of the battle, even if they constantly attack you. Heck if this is true, you could keep pretty much anything asleep while you kill it. This could be a great work-around when it comes to scripted battles (for example it lists Frankystein II as having 50% to hypnosis, so I guess you could sleep him for the battle and whoop him up, thus avoiding his guarenteed attack turns?)
Samus taught us that a girl doesn't need brains to be successful. Brains are giant, evil, and vulnerable to missiles.