mealtime battleground

Ella has seldom been a 'good eater' and she was underweight so basically I fed her whatever she'd eat when she got fussy, because I was so desperate to get food into her.  There were months where we had to syringe pureed foods into the child or she would have no solids at all!  Now I have to admit, I used to look at people's kids and swear that I'd never let mealtimes become a battleground with my child, but that's just what's happening, and I usually dread feeding her her lunch and tea .  I think now she's at a point (health-wise... she's slim, but a healthier weight these days) where I can be a little stricter to try and get the child eating properly.   If it's at all relevant, thanks to allergies she's also had an incredibly limited diet, which is only recently expanded somewhat, but still limited. 

The problems I'm having (and I'd love some advice, please!) is that firstly, Ella's a fussy eater, and sometimes, like tonight, nothing I offer is what she wants.  So tonight she's just gone to bed with only a bottle of formula in her belly, so I imagine she may wake for a bottle overnight.  Usually she'd eat pear/banana farex after all other attempts, but I got tough on her tonight and didn't offer her that since she'd already been given meat, lots of veges, lovely fruit puree, none of which were to her liking  but all of which she's eaten before, so I know she can do it. 

Secondly, she throws & drops food and prefers to crush it through her hair, highchair, clothing, etc rather than eat most of it.  I know toddlers and food are messy, but I've seen her peers eating plenty of times, and I've gotta say, Ella's food habits are really filthy even in comparison to other 1-year-olds!   So far I've tried telling her off when she starts swiping the highchair tray clean sending food flying, then removing the tray and leaving it off for a minute while she sits there bored, then it goes back in front of her and she can try eating again - if she immediately does the same to clear the tray, no more finger-foods - meal over.  Only because she's skinny (and bear in mind, I've had her Dietitian saying any calories I can get into her need to get into her), I'll then offer her some farex, which she'll usually eat. 

Advice would really be appreciated!  I have all these lovely ideas about family mealtimes being a wonderful bonding time and for now they're just ideals.  Feeding her is a full-on job and she usually gets fed before we do, so we barely even eat together as a family.