would it not be safe to turn off self-defense, are you not protected against virus/malware ? i dont remembering avast 4.8 having self-defense ... or how is self-defense working?
In general terms, it's best left on, but the risk factor in temporarily disabling it probably aren't that high, in the circumstances you are talking about.
The AV still works; if it happens to encounter a malware that is sophisticated enough to disable the AV (and there are quite a few of these around) having the self defense active might help prevent that.
The risk in your specific situation is that there is a malware in the restore point you've chosen that will activate and that has this capability. I would think that would be a remote risk, indeed.
4.8 had self defense, also.