C (gcc), 179 159 146 139 137 116 107 103 bytes

c,h;f(char*s){while(c=*s++)putchar(c),h=h%10816*104+c%27,memchr("&;@X\\ru{",h%3817,9)?putchar(h=32):1;} 

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C (gcc), 179 159 146 139 137 116 107 103 102 bytes

Edit 7: Use && on final check to replace ? - thanks jxh.

c,h;f(char*s){while(c=*s++)putchar(c),h=h%10816*104+c%27,memchr("&;@X\\ru{",h%3817,9)&&putchar(h=32);} 

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C (gcc), 179 159 146 139 137 116 107 bytes

c,h;f(char*s){while(c=*s++)putchar(c),h=h%10816*104+c%27,c=h%3817,printf(" "+!(c&&strchr("&;@X\\ru{",c)));} 

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Non-golfed new:

 char c; int h;   f(char*s) { while(c=*s++) putchar(c), h = h % 10816 * 104 + c%27,   c = h % 3817,   printf(" " + !(c&&strchr("&;@X\\ru{",c))); } 

C (gcc), 179 159 146 139 137 116 107 103 bytes

Edit 7: Use memchr and fixed a bug pointed out by James Holderness.

c,h;f(char*s){while(c=*s++)putchar(c),h=h%10816*104+c%27,memchr("&;@X\\ru{",h%3817,9)?putchar(h=32):1;} 

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Non-golfed (Which is still very golfy honestly...)

 int c; int h; void f(char*s) { while(c=*s++) putchar(c), h=h%10816*104+c%27, memchr("&;@X\\ru{",h%3817,9)?putchar(h=32):1; } 

C (gcc), 179 159 146 139 137 116 109 bytes

Edit 6: Master level code golf techniques used (commas, printf trick, etc.) - thanks gastropner!

c,h=0;f(char*s){while(c=*s++)putchar(c),h=h%10816*104+c%27,c=h%3817,printf(" "+!(c&&strchr("&;@X\\ru{",c)));} 

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 f(char*s) {  char c;  int h=0;   while(c=*s++) putchar(c), h = h % 10816 * 104 + c%27, c = h % 3817, printf(" " + !(c&&strchr("&;@X\\ru{",c))); } 

C (gcc), 179 159 146 139 137 116 107 bytes

Edit 6: Removed 0 set as it seems to go there automatically - Master level code golf techniques used (commas, printf trick, etc.) - thanks gastropner!

c,h;f(char*s){while(c=*s++)putchar(c),h=h%10816*104+c%27,c=h%3817,printf(" "+!(c&&strchr("&;@X\\ru{",c)));} 

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 char c; int h;  f(char*s) { while(c=*s++) putchar(c), h = h % 10816 * 104 + c%27, c = h % 3817, printf(" " + !(c&&strchr("&;@X\\ru{",c))); }