Should the Me262 been used exclusively as a jabo ....

[Kutscha]

.... and could they have had any effect on the Allied advance in France and to the Belgium-Dutch border?

data from Classic's 262, pg 442, Appendix 7

with SC500 bomb

normal range:
@ SL - 270km/168mi
@ 6km - 475km/295mi

max range:
@ SL - 330km/205mi
@ 6km - 550km/342mi

(radius of action is always less than half the range)

endurance @ 100% thrust:
@ SL - 0.36hr
@ 6km - 0.71hr

max endurance:
@ SL - 0.75hr
@ 6km - 1.21hr

max speed:
@ SL - 718kph/446mph
@ 6km - 750kph/466mph

To consider,

F. Wendel states in a report, "the range was insufficent to undertake bomber missions since the airfields had to be located more than 100km(60mi) from the front due to strong enemy fighter activity". (no date given but most probably July-Aug 1944)

Again by Wendel, "In level flight, the Revi is useless for accurate bombing. Pinpoint targets could not be hit. Kdo Schenk was therefore unable to claim any tactical successes".

Hitler had also ordered that the 262 should not operate under 4000m.

At this time, the Jumo 004B was rarely capable of running for more than 10hrs without a major overhaul.

There had only been 124 262s built to the end of Aug but many of these had been destroyed in Allied bombings and accidents.

At the end of Aug, Kdo Schenk had retreated to Volkel and then to Rheine on Sept. 5. This put it out of range of the Allied supply lines and just within reach of the Allied front lines.