You can't unlock it with the t-mobile SIM card. You'll need the iPhone unlocked by your wireless provider, an IEMI unlock, SIM interposer or using ultrasnOw... depending on what model iPhone you have and what Baseband it's on.
Jailbreaking and unlocking are two different things. One does not affect the other in any way. And you can't make/forge SHSH blobs since they have to match the ones generated for your device. Jailbreaking nor unlocking will affect SHSH blobs, and neither will generate/make blobs that don't exist.