He sounds very much like my DS at that age! He wasn't managing lumps either, nor could he feed himself. He was eventually diagnosed as hypermobile, and on the autistic spectrum with sensory issues, so it's worth getting the OT to look into that.
We also had to distract him to get food into him as he just wasn't interested in eating
He still isn't that interested but it has got better year upon year.
I would continue to approach this as a developmental delay, so throw out the book of age-related expectations! Not all
kids 'should' be feeding themselves or eating adult meals at age 2, there will be valid reasons why he is not, and you need assessment to find out what those reasons are
However, you can still make progress (albeit slow) by introducing new foods as part of a game (my DS loved numbers and counting, so we'd introduce finger foods that way). At his age sorting games are good too.
I wouldn't let his calories drop, nor would I suddenly stop all the distractions, just try to make it something other than a screen! You can buy funky divided plates where they can munch through a little bit of food in each section to make it to the next, or do 1 bite then he gets to hold a toy for a bit.
It's a long process, but DS was eating relatively normally by 4yo, and in the last year has got much more adventurous. The sensory stuff has also reduced considerably
Hang on in there