Cubase 64bit option/ Halionsonic SE issues

Hi, 1st time using this hope you can help,

I use Mac Air, Cubase 7 on High Sierra. this has been working perfectly until a few months ago I tried out the free install on halionsonic se3 from the se2 that I had, unfortunately i then lost halionsonic se2, and se3 was only available as standalone.

after a treacherous journey through reinstalls and issues etc. I found out it was due to Cubase not allowing the Se3 as it was 64 bit and I was running cubase in 32 bit mode.

So i took off 32 bit and halion is there now, Great!

however cubase seems to be slower and struggles more in 64bit, my main problem is that when Im using halionsonic everything seems to struggle, and I cant have any other windows open etc.

this is a pain as I like to use the macbook to video some of the playing while i record and am now unable to do that.

I would brush it off as compatibility issues with sierra but it was working fine for years.

any ideas?

Thanks in advance!