Does my boyfriend eat enough/need to gain weight?

So I guess I just wanted the opinions of some people who are calorie/health conscious. My boyfriend is 6'1" and 155 pounds but he looks really lanky and his face is especially thin lately.

Now for the past 3 days or so he has been sick with the flu so he hasn't been eating anything really though I have been making him lots of food. He just has a hard time stomaching it. But his eating has been picking up a bit again lately which is good but even when he isn't sick I just think he doesn't eat enough or understand how many calories he really needs.

I looked up how many he should be getting using this calculator and it says he should be getting 2,990 to maintain at a moderate activity level but even at light activity he needs 2,815 to maintain and he needs 1,760 just to keep his organs functioning.

Well he and I cook and eat together pretty much everyday and when we do he eats maybe a little bit less than me some day (and i try for around 1300-1600) and some days a bit more. but i don't think he ever consume over 2,300 even on days he eats a lot (for him).

Some days he'll tell me he isn't feeling well and I ask him what he ate and he'll say something like ' a bowl of cereal, a bagel w/ peanut butter, some juice' and it'll be 8 at night.

I know his BMI is in a normal range but he seems so skinny and cannot be eating enough. What do other people think?

Also I am afraid he isn't getting enough protein and that's why his face is thinning so much. (he just recently cut his beard and i realized really how thin it had gotten and it was a real shock!)

ADVICE, PLEASE.

It's his choice, in the end, if his BMI is healthy. Does he feel uncomfortable at his weight? Does he want to build muscle? If yes, look up some good plans for him or ask in the Fitness forum.

For his eating qualms, you know about high calorie, low density food. Whole fat dairy, nuts and nut butters, avocado, oils like olive oil and canola (rapeseed) oil as two examples, oily fish, dried fruit and dense fruit like bananas. Also take a look at Support Recipes and The Official High-Cal Food List. 

Good sickie foods also good to make high-cal: mince based foods like shepherds and cottage pie (veggiefy if desired), chilli, stew, soups, oils in cooking and as dressing, avocado, soft fruits and small dried fruits, fruit purees, smoothies, shakes, dense nutrition drinks, nut butters, beans and baked beans, cream based sauces, spaghetti and other noodles, mashed potatoes, porridge of all grain types, honey, jams, preserves, rice pudding, small grains like rice and couscous, muesli, sweetcorn, peas, vegetables blended into a sauce, toast cut to small squares and topped with something from the list above.

If he does want to gain, there is also The Aim is to Gain: Advice on Weight Gain, Whatever Your Reason.

If you think he is not eating enough in general, you could try and educate him about his caloric needs.