I have just discovered that my freezer has a significant amount of ice coating.
Is it safe to put meals in there for storage?
If so, what would be the recommended way for defrosting those meals?
If you have a newer freezer that is "frost free" as Wayfaring Stranger mentioned you should get your freezer repaired or replaced. From personal experience this can happen over time even with a frost free freezer, the important part is that it's the right temperature.
As far as safety, the FDA states pretty clearly that freezers must be at or below 0F. You can get a thermometer pretty cheaply to test this out. I would do this immediately and before storing any food in your freezer.
As far as methods to defrost food, there are plenty of other posts on that on this site.