OK, first things first, there's no point in setting a font around a <<set>> macro. There's no output from that macro, so there is no text to change the font of.
Second, even if a <<set>> macro did have some output, this won't work:
<span class="blink"><font color="red">
<<set $ArisaLoveFeeling to 'ERASED'>></span></font>
This is because you can't do "<span><font>...</span></font>", you would have to do "<span><font>...</font></span>" instead. HTML elements can't cross over each other like that. If one HTML element starts within another, then it has to close within that same element.
Third, if you're doing code like this:
<<if $ArisaLove is 0>>
...
<<elseif $ArisaLove isnot 0 and $ArisaLove lt 50>>
...
<<elseif $ArisaLove gte 50 and $ArisaLove lt 100>>
...
then you're witing redundant checks. You don't need to do "$ArisaLove isnot 0" when $ArisaLove can't possibly be 0, because if it was it would have triggered the previous "<<if $ArisaLove is 0>>" check. A much shorter version which provides the same results goes like this:
<<if $ArisaLove is 0>>
...
<<elseif $ArisaLove lt 50>>
...
<<elseif $ArisaLove lt 100>>
...
And finally, your bug which is causing both of those errors you're seeing appears to be here:
...
<<elseif $ArisaHate gt 400 and $ArisaHate lt 500>>\
<font color="red"><<set $ArisaHateFeeling to '8'>></font>
<<if $ArisaHate gte 500>>
<span class="blink"><font color="red"><<set $ArisaHateFeeling to '9'>></font></span>
<<else>>\
<<set $ArisaHateFeeling to "???">>
<</if>>\
The "<<if $ArisaHate gte 500>>" should actually be "<<elseif $ArisaHate gte 500>>". (Though, again, the <span> and <font> elements do nothing here, because there's no text shown inside of them.)
Hope that helps! :-)