if he were here,everything would be all right.all would能换成should吗

如果他在这儿,一切都没问题了.
all right
这是if引导的虚拟语气
1.表示与现在事实相反的情况,其句型为“ if+ 主语 + 动词的过去式（ be 动词用 were ）,主语 +would / could / might / should + 动词原形”.如：If the weather were fine,we would go to Shanghai.如果天气好,我们就去上海.（事实上天气不好） If they had time,they would / could / might go with me.如果他们有时间,他们就会（可能）和我一起去.2.表示与过去事实相反的情况.其句型为“ if + 主语 + 动词的过去完成式,主语 +would / could / should / might + have + 动词的过去分词”.如：If I had taken his advice,I shouldn't / wouldn't / couldn't have made such a mistake.如果我按照他的建议去做,我一定不会（不可能）犯这样的错误.3.表示与将来事实可能相反的假设和结果,其句型为“ if + 主语 + 动词的过去式 / should + 动词原形 / were to +动词原形,主语 +would / could / might / should + 动词原形”.如：The glass would break if you dropped it.杯子摔下来会打破的.（事实上没有摔下来） If it should rain,the crops would / could / might be saved.假如天下雨,庄稼就一定（有可能）会得救.