to get the movement of the text to slow down over time you need to probably use the ‘Graph Editor’ in the timeline panel to fiddle with your postion keyframes.
to scale the text up, animate the ‘scale’ of the text (click the little stopwatch next to Transform > ‘Scale’) by putting one keyframe at 00:00s in the time line, then one further into the clip, leave the first one at 100% and the change the second one to 150% or whatever figure works best