The top up your talking about is really a cluster feed. It is intended to aid extra calories so baby can sleep longer. Here is the sort of routine you are aiming for:
7 wake and feed
8.15 Swaddle and lay baby in cot (may take 15-20min to fall asleep)
10 Feed H
11.15 2nd nap
1pm feed
2.15 pm nap
4 feed
5.15pm catnap (40-50min)
6.00pm 1st cluster feed weeks. Dreamfeed will continue to more and less 7-8months.
7.30 Another catnap
8.00 2nd clusterfeed
In bed after cluster feed
10-11 pm dreamfeed
A lack of routine can often cause babies not settle down easily. It is extremely important to start an adequate sleep routine and using the 4s to get him to go down relaxed (p.181 BWSAYP Tracy explaines how to do this). The 4s stands for
Sitting
Setting the stage
Swaddling
Shh/patting (when necessary)
A time will increase slowly and the 2nd cluster feed can be dropped around 8 I know it is so hard to get that routine going but with a good routine you and lo with have a peaceful night. It will take time but persevere with it, it will get better
HTH and please ask if you have any questions