A Few Questions

In my quest for SY!Tiki merges I pulled a few questionable things. First off, I got an SY!Tiki that's +Atk -Def. I also got a neutral E!Chrom and a +Def-HP Lene. My questions are all about what to do with these units.
I already have a +1 SY!Tiki that's +Res -HP, so I'm not sure which Tiki to merge into. I also have a -Atk +Def E!Chrom that has been fully built up, so I'm unsure whether to merge him into the neutral one or to fodder him for Chill Def. As for Lene, I think I'll keep her since I only have one copy of her, but she is good fodder, so if anyone knows good Safeguard builds, maybe you can convince me. Thanks in advance for the help.