X2 - Good job. Getting the panel flat is the hardest job, and it looks like you got that down.
I'll admit to having a few less than full penetration welds in my work also, but this isn't a high stress panel, and I don't think you'll have issues with cracking. If you have a sandblast gun (I got one from Grizzly Industrial that has rubber nozzles and a collector bag on it), I'd recommend you blast those pits before applying your primer to keep from dealing with any rust in the future.
