Firstly I’m so sorry about your loss you have been through such a traumatic harrowing time off course this whole experience feels upside down it’s not how you pictured the start of your fatherhood journey to this little boy being. I can’t begin to understand how overwhelmed you must feel let alone doing something as huge as naming a child when the person your meant to name your child with isn’t their to help you make the right decision it’s just really sad and I’m sorry your going through this 
Concerning your son he’s so tiny as @katinka said he won’t recognise his name till 6 months plus therefore potentially changing his name to a name that feels more right for you won’t have any impact on him. You could always have his current name as a middle name and a different first name that could be an idea potentially. Maybe give yourself some more time to figure what name potentially suits your son as you do have some time.
Of course I can’t make this decision for you but I’m sure whatever decision you do make in relation to his name & anything else will be the right one for you guys. I’m wishing you & son all the best in the future.