Ok, the 200x400 and 300x300 settings only exist in SR 6.x as well not in HMP from what I saw in the in codebase.
Note the settings passed in IOTT for resln and width parameters are only applicable in the case of RAW and ASCII files as doc'ed. Thus those won't even get applied if it they were valid since the format is TIFF and thus the settings are read off the TIFF tags in this case from the file itself. I also see that the only potential way to override it were to pass the values in Sendflag of the fx_sendfax API, but in the case it will still gets ignored. So for HMP only RESHI or RESLO can be used in this case.
Btw, I check on #2 above and I get the correct values either 98 or 196 returned from ATFX_RESLN API call. Are you collecting this returned value as an INT?
For #3, there are no plans to add any features to HMP fax capabilities.
Jeff