some of these warnings are there to indicate that there is no actual processing done on them by GWWS. For example for the unsigned short type restriction like you have (value between 0 and 99) no check will be done.
About "nillable", the setting is ignored because the gateway again does not validate against it.
But it doesn't mean things aren't supported.
I could not find the documentation for the message catalogs, I will see to it that it gets fixed.
What I suspect is happening is that the message may not be formatted properly going from the client program to GWWS, i.e. GWWS expects a certain formatting and is getting something else (it might be subtle... but it has to match). This is what the TPEOTYPE error means.
Can you provide a print out of the fml32 buffer before you perform tpcall()? We can make sense of things if we also have the full MIF and/or WSDL as well. If that is not practical in these forums please get in touch with Customer Support and forward the information to them we'll take a look (make sure you indicate version of Tuxedo/SALT etc.). In the meantime you may want to carefully check the fml32 formatting against the MIF description and ensure that they match.