FCP and FID are my jam
Hello,
I think I can help you with this. We recently did similar job for another website where we had to reduce FID from around 11 seconds to 3.
For you case - it looks to be much better, but here are few notes:
1) 100ms - that is nearly impossible. Even simple raw HTML file - it takes around 50-60ms to start downloading it. That is time required by server to process your request and find a file on hard drive to start sending it out. And it is also require some time to load that file (depends on file size and network). For instance, HTML of your page is just around 20KBs. It is loaded in 6-8ms on my machine with great cable internet. While 3G network requires 200-300ms! Also, Google Page Speed goes green after around 2 seconds for FCP/FID.
2) website is optimized pretty fine, but server side caching has some problems. Some times I see that it takes 70-80ms to start getting HTML, but next time it will be 800-900ms. That also requires investigation. This might be bad caching strategy applied or your server has to serve too many requests and some times requests have to wait in queue for server to get some time to process your request.
3) there is one big CSS file which is almost not being used, but is still loaded and blocks rendering.
I hope this is enough for now and we can continue discussion in chat, if you are interested. And I'm close to 1000 characters limit anyway :)
With regards
Viktor