Seriously hon just CHILL! Most relationships do this, I've even thought myself that "OMG he wants out" coz it wasn't so "lovey dovey"... BUT its obviously not true, he's trying to connect with you by giving you lil' smooches and hugging you all the time, the fact he can fart in front of you is a feeling of trust, that he trusts you and that hes comfortable around you and feels like he can be himself. All guys fart, burp and scratch their butt etc etc, they're guys, I'm sure there are "repulsive" and some not so nice things you do that he thinks is gross, but they're your quirks, like he has his. Again, thats the same with the "penguin" remark, it isn't offensive and shouldn't be taken that way, it sounds like he's using it just as a "pet name" for you, and who doesn't think penguins aren't gorgeous/cute? Penguins are *squishable*.
And ya know what, I gained weight within a year of being in my relationship (and I'm actually the heaviest I've ever weighed) but thats because I'm so content and happy with who I am, that I don't have the pressure to be thin, blonde, leggy and gorgeous or whatever.
You say you want the spark back but you admit to being lazy, he would LOVE it and get so heated if one night you treated him to a sexy massage with lingerie on or something, seriously...
Its simple but if you haven't done anything like that recently, it'll be unexpected. To stop the rowing I'd just give him a kiss as soon as he opens him mouth to shut him up. Then he might want more kisses and the flow on effect... more luvvin' honny!