k1 timelines have been improving drastically over the last yr so USCIS 13.5 months is not a true reflection. People are currently hearing back in 5-6months (some later) They're processing mostly Oct-Nov 2023 filers right now. If you get a Request for Evidence this will obv add time
It was also mentioned ave wait time for interview is 4months, seems odd, maybe some slow embassys are skewing VJ data but for UK it's usually 2-3months (incl NVC wait). Timelines an always change and obv you could end up slower at each stage than ave but essentially, you're likely looking at ~8-10months to visa on hand, maybe less if everything is smooth.
I applied in 2022 and had my visa within 14months (but delayed interview by over a month due to travel limitations) and things have sped up since then.
I moved here in Feb, married same month, applied for AOS mid march and have EAD approved already. Travel permit and greencard are def wildcard timelines which is where spousal can be advantageous but I'm happy with my choice.
In regards to your initial concern, husband and i did the same, he filled in his sections and I filled in mine (he worked, I was at home so had more time). We had no issues with it. Evidence for us was 5 pictures, flight bookings and my i-94.
Def start getting in habit of taking some pictures as will be useful for AOS. We often say selfie for USCIS as we're not selfie people either 😂