Two Diehards Make a Glider
Total Score 669 683 753
Pattern 1 (379 steps):
x = 100, y = 94
97b2o$96bo2bo$97bobo$98bo$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$3o$2bo$bo!

Pattern 2 (126 steps):
x = 11, y = 2
o5b2obo$3bo$2b2o2bo2b2o!

Pattern 1 + Pattern 2 (248 steps):
x = 112, y = 94
97b2o$96bo2bo$97bobo$98bo2bo5b2obo$104bo$103b2o2bo2b2o$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$3o$2bo$bo!

Pattern 1 is a self-destructing glider + loaf combination where the glider and loaf are spaced as far apart as possible.
Pattern 2 is the result of searching for random disappearing patterns which can be placed next to pattern 1 to destroy the loaf, giving a valid solution to the puzzle. I generated a large number and took the one with the best score.
I'm sure its possible to do better by adding an independent diehard to the far corner of pattern 2 (or even pattern 1), but I'm done for now.