I thought I was going to help you out as these things are usual somewhat easy. However, Marvelous uses the SA-1 chip and there are several extra considerations as a result. I really don't have time to do it, nor am I sure off-hand which debuggers can provide you with reliable SA-1 BW-RAM data viewing.
So, I'll leave you with this:
That text area is DMA'd each time a character is printed with the following:
DMA: write Mode: 1 0x409000->0x2118 Bytes: 4416 (inc) V-Line:228 VRAM: 6800 (1,0) word
Instructions of interest are at $00/BF87. It will hit a breakpoint on first character print.
The source address $40:9000 is coming from SA-1 BW-RAM. Now, it just so happens the SA-1 allows for bitmap character conversion to SNES VRAM using simultaneous DMA in that BW-RAM. I didn't have time to read through the documentation and check register action to determine if it was in-fact taking advantage of this feature, or simply just doing a standard DMA from SA-1 memory space, which I believe is also allowed. To make it 8x16, you'll need to find how it gets in that RAM and alter the routine to write the next character earlier (appropriate 8x16 location instead of 16x16). Alternatively, you could attack the tilemap and that might work for you, but you're still using the same amount of VRAM which might still get you. A third option is to see how it draws the characters. Many games separate it into two 8x16 halfs and you can simply disable the second half. I didn't get to check for those possibilities either. Someone else will have to take it from here.
If you don't understand anything I wrote above, you're probably in above your head and you're going to have a heck of a time doing anything in this game that would require code modification (such as this 8x16 conversion). In addition to reading code and debug, you will at least you need to understand the basic SA-1 mapping to know what's going on in the code you debug. I imagine that's why nobody bothered to translate Marvelous yet. It's a bit more difficult and unpopular than others. Combine the two and you often get an untranslated game.