Hi and welcome to BW! Is LO quite comfortable? How are you settling her? How long have you been on these A times? I ask because she seems to be having a hard time with this and I just wonder if some adjustments need to be made. That said, when beginning with shh/pat settling can take a while
1. IN the interest of LO getting some more restorative day sleep, I would let her go up to the 3.5 mark. Are you working on independent sleep yet, if you are, I would bear in mind that these tiny LOs can get OT so easily and sometimes starting out slow and allowing some AP in to the day to keep LO better rested can help everything. Lots of Mamas do one shh/pat crib nap and then AP the rest.
2. I would feed and then go straight to wind-down and lay her down.
3. Does she want to be fed right away? How does she act upon waking? If she is ravenous upon waking, then I would surely take that as my cue and not let her go beyond that point, otherwise, I say let them sleep!
Can you get another CN in there after that 1600 feed and the 3.5 hour A to bed? Maybe stroller, carrier, swing anything that can make that A to bed less and take some of that OT out?
Keep us posted!