F-16s refuel at around 315 IAS, and would more likely refuel mid-20K. Very unlikely to be able to operate above FL280 due to non-RVSM capability of formations. Normal for a block of airspace with 2000ft below tanker for joining and 1000ft above for departing. Marsa can be declared any time the tanker is happy to be responsible for separation, generally when altitude separation is assured: declaration of altitudes or positive TCAS contact are some examples. Receivers would remain squawking until within around 3nm where they would chop to boom freq and the tanker would take control. ATP-56B is now ATP3.3.4.2. See JAPCC website for latest guidance.