Why not buy ibonds for their advantages, then put the rest in FIPDX?
Too be honest this is a better answer, but I didn't have time to address all points.
We actually have 4 completely different bond funds in OP.
1. An annuity. Doesn't say inflation adjusted, I assume it isn't? Kinda like a stable value fund except you can't get principal back.
2. I-bonds. An inflation adjusted stable value fund, basically unique.
3. A TIPS (treasury inflation protected securities) bond fund, principal fluctuates based on market conditions.
4. A regular non-inflation-adjusted bond fund whose value fluctuates based on market conditions.
These are all completely different. Although it would make sense to max out the savings bonds because they have easily the best return and especially the best risk adjusted return, after that it would be just as useful to invest in all of them, since we don't know what the future will bring. Or at least, nobody could foreseeably say to definitely use one or avoid another.
If the annuity is not inflation adjusted, I suggest use Ibonds first and TIPS second if you are relying on these for income, nominal bonds only as a dubiously useful add-on.