The D-STAR callsign field is 8 characters long. The first 7 are for a callsign (padded with spaces) and the 8th character is the station ID (SSID).
Repeaters callsigns are a maximum of 6 characters (7th character always a space) to allow for zone calls (transmitting out a specific remote repeater). Repeaters always have a station ID. In the US (and most of the rest of the world), a repeater SSID 'A' is used for 1.2 GHz, 'B' is for 440 MHz, and 'C' is for 144 MHz. 'G' is always the repeater Gateway and only used in RPT2.
So, in answer to your question, using a 2200 (2m only) should have RPT1 set to 'K5TIT C' (2 spaces) and, if you want to use the gateway, RPT2 set to 'K5TIT G' (2 spaces). To make use of callsign routing as you showed with URCALL set to another station's callsign SSID, you must be registered with a gateway somewhere in the network so all gateways know you are an authorized user.
Hope this helps.
73,
Pete AE5PL