This is off topic, but I saw your bilingualism comment up thread. In my experience, OPOL is as much a scam as “wait till they’re ready”. You already fell for one, don’t fall for the other. I’m saying this as a mom of a trilingual child. My mother tongue is very niche and most children of emigrants don’t end up speaking it.
I probably read the same studies as you and was into OPOL at the beginning but what finally opened my eyes (and helped my daughter become truly bilingual) was seeing the dynamics with teenagers in strictly OPOL families and completely ditching it.
Firstly, your main priority should be that your child speaks and opens up to you. The language is secondary. The last thing you want is to ask them how school was on the way home for them just to reply “fine” because they are tired (and they will be absolutely exhausted in maternelle) because they can’t be bothered to think in English after a day of French.
For example, I’d let my daughter tell me a story in French, say “ btw, x,y,z in mama’s language is called a,b,c”, then, if something exciting happened, I’d say “let’s call grandma and you can tell her too!” (My mom only speaks my minority language so my daughter is forced to use it.)
Secondly, you need to normalise bilingualism. Everyone speaks several languages and everyone learns new ones. If he only ever hears you speaking English then that doesn’t happen. You risk being classed as the “other”, the “foreign mummy” (especially, if your husband is French). If you’re also the default parent and do most of shitty stuff and telling off then you risk your language being associated with the negative feelings. (When I’m really pissed I switch to French 😉) The biggest leap my daughter had was when I started taking French classes and asked for her help. The second, when my husband started learning my language. We play language games, translate for each other etc.( The only thing we try to avoid is mix languages within the same sentence.)
Thirdly, it’s hard to learn to speak if you don’t see natural conversations. TV in your language is the minimum. Ideally, you’d find some English friends for play dates. Regular video calls with friends and family are good too.
Finally, they need to realise the language is useful and practical, and you need to put them in situations where they need to speak it to get something as a natural consequence - ordering a dessert on holiday, an English speaking child as a friend and so on. Luckily for you English is a lot more common than my language. Trips back home, visits by English speaking friends and family, events in English or just a restaurant with English speaking staff. The more he’ll use it with other people besides you the more confident he’ll get.