It’s one year in five, see 46 CFR 10.227(e)(1)(i).
“Closely related service” is acceptable for reneweal, if you have at least 3 years of it in the past 5 years, see 46 CFR 10.227(e)(1)(iv). If this is used for deck endorsements (e.g. time as a port captain or similar), you would need to take an (open-book) exam in Rules.
The “negotiations” are not entirely unreasonable. Notwithstanding that you are doing this with someone with limited if any experience in the industry, titles like “port captain” and “port engineer” are used very broadly and include a variety of duties, not all of which meet the requirement of being “related to the operation, construction, or repair of vessels.” The use of these titles can, at times, be similar to what’s being discussed here. Personally, I’d prefer someone who asks some probing questions over someone who wants magic words in a letter and doesn’t do anything to verify their veracity.