"Q2: Also, wouldn't depositing it now for 2018 PY count towards the 2019 Annual Additions LY for each participant who shares in the allocation of it because outside the 30 day window? If so, one participant terminated in 2018 therefore 2019 Annual Addition limit is zero for him - is there any correction available for this? The other staff member terminated at end Q1 2019... may be okay with 2019 Annual Addition limit. Will this ultimately make it impossible for the employer to contribute any PS for 2018 because of this Annual Addition issue, limiting the employer to only the SH for 2018?"
The "30 day" rule doesn't always apply. For the terminated participant, see 1.415(c)(1)(b)(6)(ii)(A) - I think this will cover you on that piece.