You can only set one customized pause gap for a burn session. The same gap will be applied between each track (which can be 'gapless' by choosing "0".)
If you wished to get more creative, you could edit the tracks in WavePad and add different amounts of silence at the end of different tracks, then when burning choose "0" as the Track Pause.
edit to add: regarding getting 2 lps on one cd - the maximum length of an lp side is @ 22 minutes. If the total of the four sides you wish to burn onto a cd isn't longer than @ 79:98 minutes, you should be fine. I have often edited tracks in WavePad to trim a project to fit on cd.
Have you already digitized the lps to your computer? Golden Records is the NCH program I use to do this.