Is this feasible? Are we on the brink of a patch that makes the game actually playable?
It seems well within the capabilities of the system, and moreover it is already in the game* and you seem like you have much of the code. Yes on both counts. Whether it might break, or otherwise render far more difficult, a puzzle, boss or similar I will leave for later discussion.
*I could probably spend the time to make the game into a version of Tetris with RPG elements but it would be a lot of work.
I am a bit surprised at the cheat searching working as well as it did. It is a simple and effective way for devs to do it but I would not expect it to work on all games. Were I doing something like this I would probably have gone directly to the sprites set a breakpoint to get handling code and gone from there, either fine tuning the build up/cool off functions or doing something like what I am about to cover.
I assume your cheat is merely of the "hold value at ? as *" type. Endless running is not then an unexpected result.
A button activator cheat would be the easy way out, assuming the emulator's/cheat device cheat capabilities support such a thing ( http://doc.kodewerx.org/hacking_snes.html
is a bit basic but if it is accurate then seemingly not) or you are willing to hack such a thing into them. Easy in this case is not bad though and even if the cheat options don't directly support it then it is still a viable choice for the hack (the other main one being the fine tuning thing I was on about earlier).
Anyway you are probably going to want to find the code handling the movement after all, fortunately you already have some relevant addresses so a bpr (break point read) set on them should find you it fairly quickly.
This will likely involve some assembly but, extra button activator aside, you are not going to be asked to have to dream up some new code so it could make a nice intro to it all. It will be more it says add 8 to this value and then this bit checks if it is above this and will do this as a result. Or indeed if start to walk is pressed do walk until run and you just skip right to run or something.
"including how fast the screen moves"
Not amazingly relevant as again you are seemingly working within the confines of the game but you may want to be more aware of camerashttps://docs.google.com/document/d/1iNSQIyNpVGHeak6isbP6AHdHD50gs8MNXF1GCf08efg/pub?embedded=true
Such a thing could actually change the camera type.
"how to make an IPS patch"
Download patch making program of choice, for IPS I like https://www.romhacking.net/utilities/13/
but others like other things.
Open modified ROM and base ROM in relevant sections, press make patch.
If you mean you want the memory addresses above as an IPS patch change then no. Share the cheat instead.