Hi Clare
Firstly I want to debunk a myth - feeding solids WILL NOT get a child sleeping through the night (I know, I know, that's what our mother's say) but it isn't true. In fact, the current standard (although it differs in different countries) is 6 months before introducing solids. Feeding solids prior to then is more likely to disturb night sleep because their digestive systems are not mature enough yet for a diet other than milk.
At 4.5 months it is probably time to look at a 4 hr EASY routine. I notice that your DD is still feeding every 3 hours. By stretching out the feeds a little bit, she will eat more efficiently at each feed. Have a look at the sample routines at the top of the EASY board for examples of common routines for your DD's age group. Generally though, 4 month olds are feeding at about 7, 11, 3 and 7, with their DF. The 4 hour routine also starts to increase their activity time, as you have considered.
Also with the dreamfeed, you might consider bringing it forward to 10pm for a little while, while you are waiting for her to adjust to the 4 hr routine. That way she will still be alseep through the dreamfeed (obviously the goal
Oh, I would think it is probably too early to eliminate the cat nap - I tried that too early and had to reintroduce it because my DS was getting overtired. I think most keep the cat nap until about 7 or 8 months or longer.
If you have any questions let me know. Good luck with it!
Jo