nickit,
When I suggested you to put extra milk at parents' place, it's not for you to go there daily to take for usage. It's really an emergency stash & you'll only need to go there once a while to rotate your stash.
As for freezing milk in ice cube trays, you can consider Milk Trays. After they're frozen, you can put them in ziplock bags.
You can invest in nursing wears - discreet & with easy openings. If not, can consider nursing poncho (but this will attract stares). I've BFed everywhere in public & the best "accessory" is definitely my nursing tank top. You can wear in underneath normal clothing or wear a cardigan etc over it. Most of the time, ppl won't know you are BFing - it looks like you are cradling baby to sleep. Just practice in front of the mirror before you try it outside & you'll be surprised how "less' there is to see. Ask your hubby to see to. It's not as bad as he thinks

Re BFing in moving car, big no no cos baby should be in car seat ALL.THE.TIME. If need to, stop the car then only BF.
Re ringsling, do give it a try. Just practice more & you'll get it right. As for baby crying when you put him in, do try again but this time walk after you put him inside. I bet he'll calm down. After some time, he'll grow to like it.
I used to wear my daughter in a pouch sling when she was smaller & she loved it

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