Wow that sounds incredible tedious, but congrats for pushing through!
I think the issue I had with the movement was that the player moved really slow and felt like his jumps couldnt cover much horizontal distance. I think the feeling the distance idea is cool and could've been done with a faster move speed as well.
Yeah I really liked that arrow part, thought it was a cool way to take the mechanic. I don't think there's any issue at all to changing the spikes back to portals after the game jam is over. The jam is done, so you don't have to try and adhere to the theme anymore. And I think that for players not playing it in the context of the jam the current iteration wouldnt make a lot of sense to them, they'd be like "how come spikes are what causes this switching mechanic?"