Relactation 3 months pp

Hi! I had a tricky start breastfeeding my baby as it hurt too much. I then exclusively pumped for about a week, but that became too draining as I didn't have a clear goal why I was doing it, so I stopped and exclusively formula fed. Then at 3 weeks pp I realised that I grieved the connection with baby through breastfeeding so I am trying to relactate. I am making about 30 ml in one day by pumping, after a week of a rigid schedule. My question: Baby is okay with latching sometimes, but will also get frustrated and unlatch a lot.. however when I put him back on the boob in those moments he will sometimes keep nursing for much longer! One night he stayed on for about half an hour after I 'forced' him back on. How much should I persevere with latching him? I don't want to make him too stressed, as sometimes he will cry at my nipple. Do you think exclusively breastfeeding is a goal I can reach? One thing to note is he will pretty much only latch with a nipple shield. Thank you for any advice or support! It can be tough to pump whilst trying to take care of baby.