1.) not a lot of compressor maps out there, especially for OEM type turbos like the IHI series.
2.) the stock TMIC is worthless IMO. If you plan on cranking up the power anyway (with bigger turbos). You have two options, either a big ole TMIC with all the proper mods (heat wrap turbo, IC sparyer, heat wrapped dp, Heat shields etc), or get a FMIC and don't worry about engine bay temps.
3.) I believe you are correct, the crank and rods are forged, however the pistons are NOT, and this is the weak part of that engine set up. Get some forged pistons and you're ready to turn up the boost. Otherwise you're on borrowed time.
4.) If you plan on pushing a higher redline, look into some JDM heads, or upgrade your current ones.
5.) Keep in mind you have extra displacement to work with, this helps with spool. THis question needs to answered with some sort of HP and max boost/RPM expectation. LIke i want to run 400WHP and have max boost by 5K RPM ETC. without that kind of info, many of the 2.5L users are having success with turbos like the deadbolt superzilla/ 20g's (mitsu base turbo). Google deadbolt turbos.